I thought of some:
-The Alice Cooper episode would upset tons of parents these days. Especially considering the plot revolves around Gonzo trying to sell his soul to the devil. I'm a Christian and I'm not offended by that at all but in this current era, I'm sure that some conservative religious parents would absolutely object to that appearing in a kid's show.
-Raquel Welch's outfits would be seen as way too sexy for a family oriented show.
-Bobby Benson probably couldn't smoke anymore. They would probably have to put something more kid friendly like a lollipop in his mouth instead.
-For the same reason as the Alice Cooper one, they probably couldn't get away with the song "The Devil Went Down To Georgia" being covered. Especially because it uses the actual name of H*ll and doesn't replace it with "Heck" or "Hades" like most kid/family shows tend to do these days.
-Johnny Cash having a huge confederate flag behind him as well as the scene where he strangles Rowlf the Dog. Both the black lives matter people and the PETA organization would try to protest those scenes.
-Using the full, uncut lyrics of Kenny Rogers' song, The Gambler. It mentions drinking and smoking, basically gives the audience gambling advice, and ends with the titular gambler character dying in his sleep. Need I say more?
-Crazy Harry as a whole would have a very slim chance of getting the airwaves. Current kid shows still have violence but it's always good guys fighting bad guys as opposed to the more joking violence you'd find on things like classic Looney Tunes and Tom & Jerry. Some folks may compare Crazy Harry's obsession with blowing things up and general destruction to a terrorist.
-The entire murder mystery episode with Liza Minnelli due to the recurring theme of dark humor surrounding death.
-Some of the songs they covered including Honest Lullaby and My Soul is a Witness directly mentioned God, Jesus, and The Bible. It's become increasingly rare to find religious references on new kid's shows, not counting ones that are dedicated specifically to religious themes such as VeggieTales obviously.
-The song Put Another Log on the Fire would definitely be viewed as way too sexist in the post-#MeToo era.
Here are some other examples specifically pertaining to Sesame Street:
-Kermit yelling at Cookie Monster, called him stupid and ugly, and saying that he's going to call his mother and tattle on him. Jeez Kermit, lighten up man! He totally had some serious issues back then. Did Kermit take anger management or something? Because dang was he easily aggravated in the early days of Sesame Street.
-The animation of two fat knees talking to each other. Some people would complain that the clip could potentionally offend fat people.
-The time they got The Simpsons to show up on Monster in the Mirror. I highly doubt Sesame Street could get away with crossing over with an adult cartoon like that. Let's put it this way:I don't think Peter Griffin or Rick & Morty will be showing up on Sesame Street anytime soon.
-The yak charging at the camera with red, glowing eyes is a little too violent and scary by modern SS standards. I should know because I personally was scared of that particular cartoon during my youth.
-Now that Pennywise, The Joker, and other such things have made the majority of children associate clowns with fear more than laughter. The live action film of the clown taking off his makeup would likely cause more shivers than giggles.
-Alistar Cookie smoking a pipe and then eating it.
-Mysterious Theater due to the fact that it copies almost frame by frame the intro of an adult oriented horror series that Sesame Street's target demographic has no business watching
-The times that the live action films depicted real children in the shower. I always knew that they were just being realistic, but someone somewhere would scream "CHILD MOLESTOR!" after seeing that. Don't believe me, Google Isaac Kappy and you'll see just how quick people are to cry "Pedophile!" nowadays.
-Likewise, Gordon walking a strange little girl down the street. Some parents would worry about the scene contradicting that stranger danger rule that all responsible parents teach their kids about.
-Depending on how you look it, some moms and dads may worry that Mr. Noodle could be a problem with kids who have issues disrespecting authority. I've even heard online reviews stating that a kid who already believes he's smarter than an adult may have negative affects from thinking an adult who doesn't even know how to eat is funny.
-Danger's No Stranger because of the scene where a little Muppet girl falls off a piano, presumably to her death. That type of humor is okay for Wile E. Coyote but not Sesame Street.
-This one is one of the few on this list that actually disturbs me personally. It's the animation "K is for key, kitten, and keyhole". The scene at the end where the kitten flies off into the sky with realistic sounds of a real kitten in danger playing always bothers me. As a cat lover, I don't think hearing a kitten crying for help is the least bit humorous or entertaining. It's natural for human beings to sympathize with sounds of baby animals in pain and it shocks me that they even got away with this one in the first place. If they had just used cartoon sound effects, it wouldn't bother me at all but the realism of the sketch makes me almost want to cry every time.
-Harvey Kneeslapper's love of pranks may be a bit concerning to parents of rebellious Bart Simpson-like children.
I thought of some more.
The Muppets:
-Some things regarding the acceptability of content in kid's show has changed since The Muppet Show first went off the year. For example, back then it was considered highly taboo to include fart-related humor in kid shows whereas now you turn on something like Teen Titans Go! and see almost nothing but fart and poop jokes. The one thing that all generations can agree on however is that profanity and children's entertainment don't mix. The song It's Hard To Be Humble from the Mac Davis episode was one of the few times The Muppets have used the word h*ll in a non-religious context. The term "one h*ll of a man" isn't considered Disney friendly that's for sure.
-The Koozebanian Mating Ritual. While obviously not as vulgar as the sexual jokes on Family Guy and American Dad, this scene was from beginning to end all about space creatures mating. I don't even think I need to explain this one any further.
-Beauregard freaking out about the apocalypse. I remember when MAD first aired a sketch called 2012 Dalmatians in the early pre-2012 2010s, they got complaints from parents saying that the parody of the disaster movie 2012 got some kids paranoid about the end of the world.
-You are always welcome at our house. Talk about childhood nightmare fuel. Am I right?
-Swedish Chef trying to skewer a turkey through it's rectum.
-Sam the Eagle's rant on televised nudity.
-While this wasn't the intention of the skit itself, I'm sure tons of children would be laughing hysterically every time the song *** Willow uses the words "***" and "dicky bird".
-Some of the songs (Time in a Bottle for example) would probably be too depressing by modern kid's show standards.
Sesame Street:
-Count To 10 with Nobody. I think the thousands upon thousands of "This used to scare me," comments on the YouTube upload of the skit speak from themselves.
-The giant rabbit chasing children. I don't find this one scary but I don't get the intentions behind it at all. It wasn't the least bit educational and almost feels like a real life lost episode creepypasta minus the blood, gore, and death.
-In fact, there are so many classic Sesame Street experimental animations and stuff like that would be a little too creepy for nowadays. The Crack Master, the train charging towards the camera, the brown and yellow gorilla screaming like a banshee, the creepy ogre face on the hill, the infamous bird animation that Dena of the Film Den refers to as "the spawn of C'thulhu himself", the singing orange, and the Whistling Beethoven bit to name a few. Back in the 70s, the animators had more freedom to experiment with weird looking styles of art and get as crazy and psychedelic as possible often leading to an unintended disturbing affect. When I was a kid in the 2000s the only scary things Sesame Street had were the William Weigman dogs and the tornado with eyes from Elmo's World. But neither of those even held a candle to the sheer horror that was '70s SS at it's most bizarre and the fact that myself, being the scared cat I was, could watch both of those scenes without even batting an eye should tell that.
-The Count counting Maria's toes. Apparently some foot fetish-related channels on YouTube got into some hot water for posting that Sesame Street clip among X-rated foot videos that Sesame Workshop doesn't want to be associated with in the least.
-Lefty the Salesman. For one, it goes back to the stranger danger thing I mentioned in the previous post. Second, a lot of people may compare his shady attitude and his reputation as a trench coat wearing swindler to that of either a flasher or a drug dealer.
Other Henson properties:
-Jareth throwing the baby up in the air during the Magic Dance number from Labyrinth. I know it was just special effects but it could be seen as being in poor taste after what happened with Michael Jackson dangling a baby off of a balcony that time.
-I found a YouTube compilation of all the times death got mentioned Fraggle Rock. I had no idea that the morbid concept of death played such a major role in a usually cute kid's TV show. If you look up "Of Fraggles and Death" it's actually rather shocking to see all the many death allusions one by one in a compilation.
-Jim Henson's Dinosaurs as a whole was more adult oriented than most other Henson properties of the '90s. While it certainly wasn't near as edgy as the types of thing you'd see on [adult swim], it still featured such gems an entire episode about the apocalypse and several uses of mild swears like h*ll and ****. The show actually reminds me a little of The Flintstones due to the fact that it was a sitcom set in prehistoric times with humor that was slightly mature but not too over the top.