You have this backward actually, the fact that Ethereum went to great lengths to design a more power-efficient replacement for PoW (rather than, say, doing something else with their lives) shows that PoW was useful to begin with.

The fact that Ethereum went to great lengths to design a more power-efficient replacement for PoW shows that the developers of Etherium derive personal value from an engagement with a technical challenge. It does suggest but doesn't prove that any permutation of the project was/is actually useful.

Your definition of useful sucks, and you should feel really bad about that. I don't get too concerned about how you waste my oxygen, but you're making me rethink that decision.

I’m sorry to hear that you’ve become stuck in a semantic bog-hole, but amused to learn that my words are so powerful that they overwhelm your conscious agency.

My point is that it is not your (or my) right to tell anyone what a good use of power is or is not. Simply because we all consume power one way or another. Expressing an opinion is fine... we can all have one of those, but we should be considerate of pot/kettle there.