I think you've mistaken what the main reason most people use Grindr for.
Grindr isn't about finding the love of your life (yes sometimes it does happen). Most guys use it to find no strings sex. The fact that the same people are there a year later is proof that it works for these people.
I'm personally a relationship kind of guy but lots of people aren't. In a way, I think grindr is great because you satisfy all the "no strings guys" so they aren't forced into relationships they don't want in order to get sex.