Well I mean, we've had the discussion before. But I know he tried to give notes about Kermit's character on the 2015 show, and it seemed like they didn't listen to his notes
Again, I think it's less that they didn't listen to him, but rather, they just didn't want to put up with him, because again, this is a common occurence in show business: if actors or performers get too nitpicky about the material they're working with, that can threaten your job security. Many a time's actors have been let go from successful shows or what have you for complaining about the material too much, and it sounds very much like that's what happened to Steve.
Now granted, Disney and ABC have made the mistakes of bringing in non-Muppet writers to handle these things, and in cases like this, I would say that Steve's notes/suggestions/nitpicks were justifiable to a certain degree . . . but unfortunately, we're long out of the days of being able to handle business with just handshakes, as Jim did - this is the corporate side of show business, and unfortunately, the corporate side could care less about the artistic or creative process. Again, it seems blatantly obvious to me that ABC bringing in writers from THE BIG DANG THEORY, THE OFFICE, MODERN FAMILY, and shows like that was their attempt to try to give THE MUPPETS (2015) a more mainstream atmosphere to appeal to mainstream audiences . . . but the Muppets were never really about trying to be mainstream, and Jim was always wanting to raise the bar as far as puppetry and everything else is concerned . . . but that's not how Disney or ABC or any of these big corporations operate, so they're not going to go that route, and as such, decades-spanning franchises like the Muppets are suffering as a result, because they're not being allowed to do what they've always done their own way.
So again, it's a two-way street: one way, you have the integrity of the Muppets on the line because you've got writers who don't know how to write for them, and directors who don't know how to direct them, and this is supposedly what Steve was speaking out against. The other way, however, you have studio heads, network executives, and suits who don't want to put up with any complaints, whines, nitpicks, or anything like that, and if any of their subordinates do this, they'll look for any reason to fire them.