At which point being unable to solve it because it's uneconomical is a form of being unable to solve it, and the centralized system forfeits the alleged advantage.
Sometimes the problem doesn’t get solved because it is lucrative to not solve it… not because it is too hard/costly to solve. Ie: some platforms don’t internally classify spam/bots/corruption/scams/etc as a problem. Often, the right amount of it increases engagement… and thus the perverse incentive perpetuates or amplifies the problem.