I solved this in the past by creating a meetup. It worked every time. Also, i fail to see how this is an “Uber for”. I see it as a niche(sports) Meetup app.
That's fair. It's an unbundling on Meetup. Meetup is great but as it's not specific to a sport it doesn't solve the problem that well. When you go to a Meetup the games vary in quality (bad fields, late organisers, not full games), having a sport specific app with quality review solves this.
And I agree "uber for" can be misleading. It's to show that the games are on demand. In the same way at any point you can go to a gym, you should at any point be able to find a full well organised sports game of your choice near you.
the "on demand games" can be a unique selling point