I'd argue that the least number of users using blacklists would be the best case for the ecosystem. I agree wholeheartedly with the concept that good content will still shine even if people begin shitposting. That being said limiting user's voice will diminish the number of users willing ot invest the time it takes to using the platform. People just want a place to post without limitations more than anything is my experience.
RE: What do you think would happen if all "formal" abuse fighting services stopped?