Taking Seinfeld specifically, his complaint is bullshit. These are the two examples he has given (in multiple interviews):
(1) He makes a joke about people scrolling through their smartphones “like a gay French king” and getting a negative reaction.
(2) His teen-aged daughter reacted to a statement by her parents that she might like to “hang out with boys” by saying “that’s sexist.”
In neither case does Seinfeld have a valid point about “cancel culture” or political correctness.
In the first case, it’s just a bad joke. What “gay French king” is part of the public consciousness that a hand gesture will evoke that image? There is none. “Gay French king” is not a thing. It doesn’t evoke any associations in my mind. That makes it seem like “gay” (and “French”) are supposed to be intrinsically funny.
It’s true that maybe a decade or two ago, saying “gay” by itself might have been enough of a joke. And it’s true that society has changed to the point that calling something “gay” isn’t intrinsically funny. But that doesn’t mean that society has lost its sense of humor and Seinfeld is now risking “cancellation” because people didn’t like this one joke. And it’s certainly not some fault on the audience’s part that they didn’t find this joke funny.
In the second case, middle-aged parents embarrassed their teen-aged daughter by bringing up a subject of a sexual nature and she reacted in panic to shut them down. This is nothing new.
The other comedians I’ve heard complaining about “cancel culture” and political correctness–some of whom I like a lot, like Dave Chappelle and Bill Burr–are just being whiny assholes.
The people who have been “cancelled,” if you want to use that term, are people who have actually harmed others, like Bill Cosby or Louis C.K.
Louis C.K. subjected several women to unwanted an non-consensual sexual acts and then his management team sabotaged their careers. That’s reprehensible. It’s not drugging someone and raping em like Cosby did, but it’s still something bad. And C.K. hasn’t even really apologized for doing that. Instead, he’s gone on stage to complain about how he has been treated.
Someone like Shane Gillis was hurt by his own actual racist statements. They weren’t failed jokes; they were actual racism.