"If Bitcoin ran on solar panels nobody would give a shit."
If you told someone that bitcoin mining uses more power than all the solar energy harvested throughout the world I think most people would say its a waste.
Those people would say its a waste because they're imagining energy as a medium for the delivery of physical things. When energy fails to deliver something physical, they view it as a waste.
Money and value are social abstractions, not physical things. As an example: without trust in a government, fiat money would not function, and would become valueless.
Energy is the link between the physical world and the social-abstract human world.
I think it's a waste because that energy could've went to more productive on-demand energy-intensive uses like electrolysis, desalination, or carbon capture
That's false because the energy capacity for those things was there already, and those things did not grow and proliferate to consume energy the way you see Bitcoin consuming energy.
The problem with those processes is no one is willing to pay for them, ie. no profit incentive. That is a separate issue involving public spending and creating incentives to support industry.
What you've done is imagine ways to spend money/energy that isn't yours for a greater public good, which is pretty easy but otherwise overly simplistic.
Many people consume things others perceive as wasteful. Value is subjective. If consumers didn't value their purchases, they wouldn't buy them. There are some who say commenting online is a waste of time, but here we are.
Money and value are social abstractions, not physical things. As an example: without trust in a government, fiat money would not function, and would become valueless.
Energy is the link between the physical world and the social-abstract human world.