Its funny how many folk near the end of their own lives express similar opinion as yours. It was you/we of the older generation that created the unsustainable world of bullshit business (Graeber, Bullshit Jobs, extended), that the young are faced with.

It's us holding the purse strings that need to change it.

Shutting down the bullshit businesses that use massive energy to perpetuate everything profit is made from, including war, death, and disease, would be a good start.

That done, there will be no need for depopulation.

We actually do need all hands to the pump, when we switch to solar, because this is the only way to get entropy back down. Lots of people, as many as possible, doing things, anything, with the energy of the sun other than just letting it go to heat.