I too really miss the old OKCupid. I was on it from near its inception (around 2003 I think) until they started requiring phone numbers (2020 I think) and I agree its decline was tragic.

That said, I think the world has changed in ways that would make it difficult to replicate now. For one thing, imagine all the AI bot profiles that would exist. For another, the legal environment has only gotten worse in the sense that entities like Match will try to sue you for infringing on some bogus patent.

Also, let's not forget that the takeover by Match was a deliberate choice: those "140 IQ dudes" chose to sell out their nice product to a big evil company although it was pretty foreseeable they were going to ruin it. Who's to say that wouldn't happen again?

That's why you gotta make it a not-for-profit.