Never seen spam in Meetup. I hooked up my personal calendar with Meetup and it added quite a bit of events into my calendar which was a bit spammy but it's only because I had told Meetup I was interested in all that stuff and it was easy to shut off and filter out.
WeWork bought Meetup recently so I don't know if any of that will change now.
It isn't free to set up a meetup on Meetup.com though (which arguably helps keep the spam away).