> So far no-one has been able to point me at a single thing that public public blockchains do that either is worth doing and is only possible using blockchain tech, or is better (more power efficient, faster) than using pre-existing technology.

Facilitating certain types of illegal transactions. Ex, Sanctions evasions for the average Moe, online illicit substance transactions between complete strangers. So I would guess the crux of your statement is actually the “worth doing” part.

I respect your position but I respectfully disagree.