The problem with Reddit as a business is that they have the least profitable users of any social platform. So one would have to build a backend, incentive the app makers to switch, get advertisers and do it all more cost efficiently than Reddit does it.
The business model can't be "become a giant social network that makes billions and employs tens of thousands of people."
If the whole thing is lean, with minimal costs, no account reps, and essentially non-profit, it's a lot easier.
Of course, that means it goes one of two ways:
1. Never gets traction, dies after a bunch of work
2. Takes off and the people controlling it (rightfully) want to be compensated for their hard work, so they start adding advertising and focusing on monetization, which requires hiring more people, which requires a more mature business model, which heads towards IPO.
That’s a small needle to thread.