I understand it's wasteful, of course, but waste in a ecosystem of vast abundance seems like a feature, not a bug.
The problem is that it's not a ecosystem of vast abundance, just occasional abundance. Literally no-one in the world right now is sitting on a constant supply of TWs of excess electrical power and saying "golly gee what are we going to do with all this". Perhaps France got closest in history and their prices still aren't "too cheap to meter".
You can "waste" the power (either by actually "burning" it to heat and dumping it, or just disconnecting the solar panels), but then you'll be short of power later and need to fall back on something expensive or with high externalities. It's also bad in terms of the capex for the solar panels (assuming solar), as you can't use your expensive plant as much as you want. If you can you'd rather use "$10" of energy that you can't sell to store and sell it later, even as heat, at any price than just lose it all.
Even if you massively, massively overbuilt solar and wind so that you were in a "vast abundance" scenario on average, you still have to store some of it for night and/or winter.