A lot of people (including SA posters) say it's not as good as it used to be, but that may be the same phenomenon HN users complain about when they say HN used to be better back in the day.
I'm still active on Ars Technica but the constant political sniping allowed there is really tiresome. I could happily live the rest of my life without seeing "snowflake" used as an insult again. Or without seeing a snarky anti-Trump comment in an unrelated article with 70 upvotes. I don't like Trump either, but that doesn't mean I want to read lazy insults against him all day in every discussion. Reddit's never tempted me to register an account though I like to read Ask Historians.
When I look at SA today it just seems juvenile and try-hard. Really, painfully unfunny.
I think part of it has to do with the stricter moderation; SA in the early 2000s was 4chan before I knew there was a 4chan, and I appreciated the raucous, sometimes offensive humor.
Moreover though I think you're right, SA is still SA. My ideas about what is funny have changed, but SA is still the same.
this is how trends work. the originators are truly creative and interesting, but over time the paths they forge spread across populations, and inspire increasingly poorly executed knock-offs. eventually it becomes embarrassing for earlier adopters.