The way I (and others in my group) used Meetup was this:

1. Schedule a meetup to meet players ( soccer, in my case) and organize a game at the local ground.

2. Repeat Step 1 for 3-4 months

3. We now have enough regulars and switched over to Whatsapp. Easier to coordinate, schedule games, manage rosters and because Whatsapp is so ubiquitous, you don't need to download/track one more app/website.

4. Exit Meetup.

It was similar for other activities too - board games, AI/ML groups and so on.

Meetup was always going to struggle with a viable business model this way. Groups of people once formed into groups will drift away to more familiar, informal ways of staying in touch.