I guess OP was using the user centric approach of measuring success, however naive or ir realistic it is nowadays.

That's the problem: ad based apps want to keep you there, not solve your problems.

I thought about a dating app where you pay for entry and that's it. Then the incentive is that you don't need it anymore ASAP, because the more time you spend there, the more costs.

Theres a network problem, where it must be high quality, successful, and with lots of people before people are willing to pay. Maybe it would need to start with a free trial in a small region to get some traction before, and rolled out slowly.