A big flaw in dating apps is ... people. They tend to keep swiping and never pick a partner.
This is because dating apps turn out to be bad for actual dating, which is sort of obvious. If you want a quick fuck, technology can help you find people also interested in that. But for something deeper, you need a more personal connection. This can be found online, and may even be easier online than in person if your parameters are quirky enough that you can't get hits in the local dating pool. The nature of dating apps, which rely on ease and speed, directly undermines the needs of forming a relationship, which benefits from a slow approach and multiple contacts over time.
Another fact is that most people are simply bad at mate selection in general. There's a tendency to search for "the one" when most people have a wide range of possible mates that would be compatible. Only someone with a very odd combination of traits will be looking for a needle in a haystack. Most people only need to look for someone with sufficiently similar interests and life goals. Trouble is, they're rarely looking for that; they're looking for a hot fuck. This also is counterproductive to finding a good lifepartner. There's a reason why so many historic societies (and a few modern ones) relied on matchmakers, and it's because thinking with your crotch tends to have bad results in practical and emotional areas. Better to have cooler heads sort through a range of possibilities and present one or a few candidates who meet your general criteria (suitable age, religion, good provider, etc.) and then get on with it.
Of course, another factor is pheromones. This is easily handled when people are within easy reach, like students on the same campus. You may have to account for
birth control pills modifying tastes, but at least you've got close contact. Online relationships lack that vital signal, which can be a real problem if it's meant to be a breeding relationship, and sometimes an issue even if it's not.