I think the parent is suggesting that there is the same or more sex, just for fewer people. If you can access a thousand people in your league there is no reason to look outside of it (we're all min-maxing) whereas before you were limited by vicinity.

I understand tinder has become more of a dating app than a quick hook up one these days anyway. At least that's what friends tell me, I prefer getting drunk in a bar the old fashioned way.