If you're asking why we would want to progress as a species, I suppose that's a rather subjective question. I like the idea of materially improving the lives of humans. That includes scientific discoveries, curing ageing and other diseases, space exploration and interplanetary colonisation, material abundance like unlimited food, etc. We don't achieve this unless we make major technological advancements, and this requires major new sources of energy.

Civilisational levels are defined by orders of magnitude in energy use.

Says who?

Why shouldn't our civilization be defined by how efficiently we use the energy we gather? Or the lifespan and health of our citizens?

Claiming that the sum of a civilization is how much energy it controls is just a meme from the 50's. It's a shitty, short-sighted metric. One that would consider building a nuclear reactor and dumping the power into a bank of resistors as contributing "more progress" than growing abundant food, or protecting the ecosystem.

It's our civilization, we can define progress however we want.

Practically, at the current rate of CO2 emissions we’re going to be needing that electricity to do carbon capture eventually

OP has literally been playing too much civ and believes that tech trees are destiny.