I have to say Elton John.
The problem with the PC aspect of criticizing celebrities is their connotation with virtue. Elton John seems to be a paragon of nice, but his performance seemed like it had overstayed.
I had a negative view of Elton John when I was young, although it wasn't really based on his work. What triggered me were some articles about him in some publication aimed at elementary school students. Can't remember what got me--just that there was something.
I mellowed out a bit when I got older. I got a "best of" recording at Goodwill. Someone apparently liked it--the LP was really, really worn when I got it. I found some of the photos on the sleeve a bit too much for me--but it was a different era. I kept the LP, although it's not one I'd keep if I had to downsize to the 10 LPs for a desert island!
Probably true of any performers. Many seem to peak at some point at some early year and that's as good as it gets. I'm surprised at how I research old TV shows, and see some major actor in that show who continued acting, but never had what they had in the TV show that made him or her a household name.This same staleness pretty much followed almost all the megastars, going back to Elvis, Sinatra, and probably before. Mae West and others essentially became living parodies of themselves.
It's not universally true. I think stars like Ella Fitzgerald and some other icons were terrific until the end.
I suppose one problem is a fear of doing something different than what brought success. And I suppose there is what fans like. I remember reading that Neil Diamond's live performances had a lot of content from his early years, and supposedly that was what fans wanted. You wonder if he ever felt: If I sing "Solitary Man" one more time, I'll be in solitary confinement!
I have a lot of respect for Miles Davis. I don't know that I have what it takes to appreciate a lot of his work when I hear it. I don't think I have the right level of sensitivity or something. But intellectually, I really admire how he was able to change and evolve.

