Keep in mind that the parent stated multiple conditions in the problem and your "obvious solution" only addresses the "too many resources" component.

Doing "useful work" is obviously better but still doesn't address the "fair say in decentralization".

>I'm trying to design a system where something like 95% of the work goes to useful computation, [...] It's a hard problem.

And to make it an even harder problem, also try to design a cryptocurrency system where Bill Gates' billions to buy supercomputer hardware has no advantage over a typical homeowner with a cheap computer. Maintaining _economic_ decentralization is very hard. I'm not aware of any decentralized protocol that has solved it. Heck, most whitepapers about decentralized protocols don't even explicitly discuss it.