I'm often thinking about building a better Meetup, it's so expensive for organizers these days. But then I acknowledge the network effects and I give up. And they own Eventbrite too! Savvy people.
Partiful feels like it has replaced Facebook Events, Meetup, and the other formerly-popular hubs for in-person event planning.
I see a lot of people using https://luma.com/. I'm sure it's not as big as Meetup but it does have a decent community of users, and you can set up pretty much anything with their free plan.