Earlier quoted context omitted.
nah, there's approaches. I meet with politicians and suggest a carbon tax on crypto exchange conversion to fiat - miners have to cash out, after all. You have to tax the clean coins too, otherwise buyers will just exchange dirtycoin for cleancoin before cashing out.
Why not tax or make all energy more expensive? That way all wasteful usage will be curtailed and only the valuable use cases will be left after a while. If we do what you proposed it sounds like we should start taxing other behavior on the internet based on its usefulness to society and electricity usage.
That said, it's not enough - because the market isn't some NP-complete-problem-solving magic oracle. It's just a greedy optimization algorithm. It's very prone to falling into bad local optima. We know that for a fact, that's the basis of most regulations around markets. Left unattended, the market would happily prioritize mining Bitcoin over producing food, as running Bitcoins in circles is more profitable than selling grain - up until there's an actual shortage of food and the market self-destructs.