I was the same. Meetups are not as helpful as groups where you actually do an activity together, be it theater, climbing, board games, ...
The problem with meetups is that you don't have the common activity to help with really interacting between each other. It's often a presentation and then some networking but networking events at meetups don't help introverts at all.
OP: it seems like it's time to seek professional help. Your post implies worries about your mental health. Time spent regularly seeing a counselor is probably going to the be most effective thing for you.
Tech meetups are not the best choice for meeting people. Try movies, museums, hiking, etc. Meetups where there is a built-in social component of perhaps one where conversation is the whole point.
The problem with meetups is that you don't have the common activity to help with really interacting between each other. It's often a presentation and then some networking but networking events at meetups don't help introverts at all.