My feeling is that we're losing the facilities to make general friends, and that void is being filled with the non-optimal but best-you-can-do interest-based groups. This is even more effective on the internet where you can find even the most niche group that may not have been possible when we were limited to our local area.
In short: Meetup is good for activities, but it doesn't fulfill the third space OP mentioned.
(This is my experience, YMMV)
The Meetup platform is pretty terrible. It’s designed to get people to join many groups, most of which they never engage with and just get a lot of spam from. I’m sure >99.99% of pre-pandemic “social” Meetup groups were totally inactive. Most of the rest would have semi-regular events that <4 people would sign up for.
That said, I think there’s a lot room to build a better version of Meetup.com. The main problem with it is that the managers just don’t know what they’re doing, or are in too deep with tech debt and legacy code. If someone here actually wants to build a better version of Meetup, let me know.