One problem is there are people that post the same event multiple times. I documented one where they posted the same event 22 times. I'm not sure how they even do that. One way they do it is just to post the same event 5 minutes apart so looking at the list of things to do the same event appears over and over. All of these are the same event: https://i.imgur.com/o4fAxjA.png and there are plenty more of the same event further down the page. But it's not just different times. https://imgur.com/C1gMleC
I've seen one event which is clearly fake. It's always full at 101 attendees from the moment it is posted. I'm not even sure what the point is except maybe to harvest names from a waiting list? Like maybe the idea was if the meetup looks popular people will try to join? The event is clearly a marketing event (not about marketing itself, but an event designed to sell attendees on a service)
Another issue is just bars effectively listing that they're open. I don't know how to solve that. It's one thing if it's really a "meetup" like "model rocket talk at Bar ABC" but some listings just come across as "we're open"
The other big issue with Meetup.com is email spam. They have like 40 different things they can send you email for PER meetup and attending any meetup signs you up for all 40 things. I get that I might want to know about meetups I've been to before so maybe that's okay? But... They also end up signing you up to categories of similar meetups and so if you ever attended a new meetup you'll get added back to the category. Which I also get. And it might be fine except at literally 65% of the email I get daily is from meetup.com at this point. So it feels like something is clearly not working.
The finally issue I've seen is fraud? I've seen a meetup where the user kept posting things like 250 people have signed up! Hurry now! And then the next day 350 people have signed up for our party!!! The final count they claimed was 600 people but the venue only legally allowed 200 people. I brought it up the venue only held 200 people (listed on their website) and the guy just asked if I was attending his awesome event with 600 people.