As 4chan showed in the past, user bases go to platforms that allow NSFW content, and take their SFW activity with them.

But that didn’t answer my question. What problem does age verification genuinely solve by taking away my (adult) privacy?

PS: Expect a lot of LGBT+ content to also get flagged, as it’s considered inappropriate in certain authoritarian countries with money. Having to send in personal ID to join a minority community is just one step away from wearing pink triangles.