I think we could say that covid killed a lot of these activities (some were already in decline, but covid delivered the final blow). GenZ just happened to be coming of age during the pandemic years and thus prefers to stay home as they see that as normative. Millennials are past the rave stage as they're getting into their 40s.
As a Gen Z who was a shut in long before COVID, I disagree. I knew plenty of people who loved going out before, during, and after lockdown. I'd guess only a fraction of people who liked going out before found the joy of staying home. But likewise I'm sure there were some who found it miserable at home and after lockdown vowed to be more outgoing.
I hesitate to write a lot of things off to COVID because, if you look at some presentations/papers from early on in the pandemic, a lot of things probably changed less than the "experts" thought they would. That said, I also see various things that were on a downward trajectory or cruising on momentum being given a downward shove by COVID.
A friend who used to run big late-night parties in San Francisco said the big change started after the 2008 recession. Many of the twentysomethings who were laid off left town, and the ones who remained were working longer hours.
I was on the scene in the Bay Area in the 2000s. I went to warehouse parties and secret raves that required calling a number to find out where to get picked up to keep the location secret. It was vibrant and a lot of fun.
There were at least two sites that I knew of for keeping track of parties (bayraves.com was one, I don’t recall the other). The scene was dying at the same time that I was aging out, but I sure miss it.
When I lived in the Midwest, the scene died when ecstasy became a known quantity in mainstream news media. The last rave that I went to (there) was loaded with a million cops. An org that offered free testing for purity / adulterants was told they’d be arrested for testing any pills. What a backward and unhelpful position to take when people may be at risk of an OD. Ecstasy was still generally clean at the time. I’d be afraid to take an unknown pill today, what with fentanyl and the like.
My wife, who has been a raver since the 90's, is currently out collecting free Narcan doses to deliver to people throwing raves in Southern California. Party organizers need to really step up and have Narcan on hand, but most don't.