I remember the 2009 episode that they tried to legally change the word fag to mean obnoxious harley drivers. But I think they don’t they really use it much anymore. I don’t really remember it stopping so did it just fade, am I mistaken or did they get censored some how? I recently started watching from the beginning and they use it way more.
It fell out of fashion with a few things:
Legalization of gay marriage - they pay attention to politics and probably also know the increased violence against gay and trans people since then
More pushback on the f-slur itself, as early as The Office US’s third season in 2006
Comedies like The Hangover trilogy getting called out for using “the joke is being gay is sick and disgusting” rather than using “gay as synonymous with bad taste”
More sympathy for perspectives outside of themselves - The Hobbit is a good example. They would never make the crab people episode today
Considered dead/old hat when Family Guy stopped making those jokes in their Trump parody episode, so SP was likely done with it for way longer.
I’m not a fan of South Park’s boomer humor the last few seasons and especially Tegridy, but I do think they were using it as a colloquialism rather than a slur. Kendrick Lamar said the word a lot in Auntie Diaries as a way to apologize for it, and that came out in 2022.
Calling things gay is honestly such a stale joke.
TL;DR things change, and it’s a cultural shift in American language more than any lightened homophobia in the world