I think the impulse to promote all meetups was a good idea but now adding to much noise to the "PROMOTED" feed. Of the 10 "PROMOTED" feeds 8 are adverts for meetups.
I propose adding Meetups to the navigation bar and only adding them to "PROMOTED" when they are especially significant; for example have a special speaker and might draw attention from people who are out of town.
Would an opt out option in your settings be enough to satisfy you? As well as an additional rss feed that did not include meetups?
That way people can opt-out rather then requiring people to opt in to receive meetup notifications.
Would this solution be satisfying you? Do you think it would satisfy the community?