Even when it aired, it was walking the line of generally offensive. That line didn’t have to move far to tip the show out of favour on average. Seinfeld himself addressed it, initially being upset that his brand of comedy was falling out of favour, but eventually coming to terms with the fact that he himself was out of touch and would benefit from adapting.
https://www.nbcnews.com/pop-culture/celebrity/jerry-seinfeld-said-regrets-comments-blaming-extreme-left-ruining-come-rcna175678
Hopefully that link isn’t broken or bad. But yeah, he basically said he was wrong and out of touch. And that he could stand to make an effort to get with the times.
His style of comedy has always been about finding where the current edge is and seeing how far you can cross it and still be funny. But the drawback is that the edge moves. So you have to keep seeing where it is, and what you said 10 years ago probably isn’t funny anymore. It’s normal to get frustrated when something you put effort and work into is no longer seen as a good thing even though it was liked well enough at the time. But he really should have expected that result. And I think he knew that when he made it, but had since got caught up in the false validation that can come from being out of touch.