Like this?
There is no reason for Arthur to be that creepy. The lizard tail and tongue aren't even the reason why.
But it at least felt organic. I've seen lots of Flash animated cartoon shows that get it... Teen Titans Go, Wander Over Yonder, the new Tom and Jerry cartoon... even 9 Stories other 2 PBS shows, Wild Kratts and Peg + Cat. Maybe, just maybe the style of the show wouldn't lend itself well to Flash anyway. At least, the stiffer kind they're going for.
Then again, you look at the shows Cookie Jar turned to Flash at the same time when WGBH was about to part ways. Caillou, Hurray for Huckle, Johnny Test (which was actually passable when WB was producing it), and worst of all, Doodlebops Road Show. Stiff, ugly, cheap. I'm surprised they didn't inflict that on Arthur sooner. So, it could have been much worse anyway.
But animation aside, the quality of writing is inconsistent. Long runner do tend to have this problem so I can sympathize on that level. The writing was starting to suffer (again, due to age) several seasons before the animation change over. But these last couple of seasons have some really painful moments. Ladonna (who I'd admit is getting better) was introduced Poochie style to the cast. While she does have some stand out good episodes, she comes across as yet another unnecessary addition to the cast. Not as painful as Binky's adopted sister in the ones where Kate and Pal can talk, which aren't great to being with (with certain exceptions)... but to add such a nasty, obnoxious, unlikable character to them makes a bad idea
worse. Mei Lin Takes a Stand is just painfully unwatchable with her nonstop attitude.
Not to say there weren't some gems, like the one where D.W. throws a wedding because she saw a reality show, the super hero creation one (if you can look past the Commercial Free Childhood-like Author tract, and the hypocrisy of saying comic book characters were only created to sell you things then saying how great Jack Kirby was), the hilarious episode where Buster's Dark Bunnymobile keeps getting set off in school... even some current ones, like the aforementioned Brain's Ice Cream War (or whatever it was called) episode. There are still some fun episodes left in there, but it doesn't make "In My Africa" or "So Funny I forgot to Laugh" suck any less.
So Funny is one of the worst. Not only is it followed by a clip show (making the current animation look awful next to the more fluid classic clips), but the whole episode is poorly written and anvilicious. What's wrong with it? Muffy and Francine's complete hypocrisy (which is never called out on), Arthur's strange passive aggressive streak (that's more of a Fern thing), Sue Ellen overreacting (she gave Arthur a friendly warning
once and then went straight to Ratburn when a second, more serious warning
wasn't given), and Sue Ellen's strong character turning into a weak, emotional wreck, instead of someone who'd fight Arthur over it. Just all around a terrible episode that ignores character and continuity for a cheap message that they can't even deliver straight.