I've been going to a lot of meetups (from meetup.com) in the past year, and sadly I've come away pretty disappointed, for a number of reasons:
1 - I'm just not in the least bit interested in the overwhelming majority of meetups out there. So there really aren't a lot of interesting meetups for me to choose from.
2 - Way too many of the meetups are actually businesses in disguise. They're looking to sell you a class or get you to pay admission for an event. This might not be a big deal for someone with more disposable income, but it is often a deal breaker for me.
3 - Most meetups meet for just the event itself, and everyone leaves right afterwards, leaving no opportunity to interact with the people there.
4 - For the handful of a handful of meetups which are interesting, not businesses in disguise, and actually leave some time for interaction before/after the meetup: apart from the single shared interest that we all presumably have in the subject of the meetup itself, the people you meet are going to be pretty random and so the odds of making a genuine connection are still going to be pretty low, in my experience, especially if you're shy.
5 - Usually you don't see these people again until the next meetup, which is usually a month later. So you talk to these people maybe for an hour a month. Not much of a chance to make a connection.
Overall, I just really haven't had much luck with meetups, in terms of making friends. I've done better with dating sites, honestly. At least with those, I can be pretty sure before I even go to meet someone that we have a whole bunch of things in common, and can pretty quickly sense if there's some chemistry between us, and if not just move on to the next person. It's harder to do that with random people at meetups. Just my 2 cents.