Maybe we will rise to the challenge and go green on these, I'm not convinced yet but I am definitely not ruling it out.
When it comes to optimism, it boils down to two distinct modes. Necessity is the mother of invention. Less energy, stuff and stimulation will be good for most people in wealthy countries.
Fossil fuels will decline, we will make some cool new stuff that makes that decline easier, we will demand less stuff and use of energy. This doesn't sound so bad. Hopefully we will move into something akin to Solarpunk + cottage core. A declined future that is more fair. But the pessimist in me feels like that is but fantasy.