I don't think the argument is focused on what Meetup should do, but what they could do if new user acquisition were a priority. It's a growth tactic that can be balanced with retention and engagement approaches, that Meetup right now understands and is heavily investing in.
Taking this approach also doesn't mean you'd have to go full throttle. You could test and decrease the pace by only allowing a segment of quality organizers the ability to create their own app.
I would say that the OP is looking at the wrong metric for meetup's business model; it's not mobile traffic that counts, it's contacts per user per month[1] that tells meetup whether they're succeeding at building lasting relationships.
1. This would actually be a weighted moving average of the last three months and another of the past year. Obviously, not the only metric in play.