>Crypto is so inherently wasteful it's completely unethical.
skateboarding is inherently wasteful, should we ban that too?
if people choose to do something voluntarily, and devote resources to it, I don't see a basis for you declaring it unethical. If climate change is your fear and we all decide to save ourselves by living in caves, some cavemen might still choose to engage in the cave-crypto-currency equivalent (carving big giant rolling stone coins?): it's not unethical, it's just not what you would choose.