The question shouldn't be "how do we stop this company", it should be, "why aren't people providing competing, non-crappy, apps?". Let's fix the root issue rather than proposing regulation to regulate a problem that shouldn't exist.
The features that make an app crappier are what makes it sticky and lucrative. Making an app better at matching people is expensive, but doesn't give you revenue. The owners heading in that direction will get offers from the crappier, more profitable app maker that are hard to refuse.
With the existing hegemony of Match, a new company doesn't actually need to worry about becoming profitable; if they can be good enough at matchmaking that they start to catch on, then they can rely on a buyout from Match. Much like how a decade ago, "getting bought by Google" was the business plan of a lot of companies, many of which did get acquired by google.
Side advice: never use the words "free market" in an argument, you get dismissed immediately because people are instantly compelled to think of reasons that it isn't a free market.
Hypothetically yes. But why do we still pretend we're in a free market. That is so self evidently not the case.