Nah, it’s because it’s less of a headache than Mastodon (everyone I’ve talked to likes the idea, but hates the implementation because they find it hard to navigate) and it’s not a mess like Threads or Twitter. What people want is 2015 Twitter because they’re not nerds. They want it to just work.
As for the invite-only thing, I found it odd at first, but I kinda understand why people like it now. It makes it harder for assholes to join and if they do manage to get an invite, they’ll have to get another one after their account gets banned for bigotry or being a shithead.