>All energy and computing resources used on mining Bitcoin are spent and cannot be used for anything else.
Bitcoin mining can be used to monetize excess energy (especially with renewables) that would otherwise be wasted, so what you said is not entirely true.
The statement you quoted is true, regardless of your assertion. As for addressing your assertion by itself:
Energy storage and distribution networks constantly strive to minimize unstorable excess energy. Even under the assumption that that will not happen sufficiently, or, less hypothetically, by only taking into account the currently achieved levels: What you propose cannot be enforced. By design.
Bitcoin is decentralized, and everyone with an Internet connection and energy available can participate. That includes anybody with an even mediocre Internet connection and access to precious resources that can be converted into a single Bitcoin block and a massive amount of heat, for personally enriching transaction fees and a block reward in return. One of Bitcoin's very core principles makes gapless regulation unlikely, if not impossible.
What is your proposal for guaranteeing that only non-storable, non-transmissible excess energy is used for Bitcoin, other than individual goodwill?
Bitcoin mining can be used to monetize excess energy (especially with renewables) that would otherwise be wasted, so what you said is not entirely true.