I don’t think much has changed in this regard, comedians are very often miserable complainers... in the past they usually just didn’t get frequent tv specials or series.

And to Seinfeld’s credit, his show seems to be intentionally more of a talk show than a comedy show. Bill Burr has ALWAYS complained about sensitivity (kind of a Denis Leary sibling), Lewis Black’s shtick is angry ranting... it’s an entire genre.

Comedians previously ran for much longer on much less material, at least as far as I can tell... and yeah sometimes if they had bad days they’d rant for their entire set... you just didn’t see it.