Techno-optimism has always been used to criticize this attitude, together with techno-chauvinism. Techno-utopianism is a less loaded term that might encompass more positive visions of technology, like the attitude towards space exploration in the 60’s coming from the soviet union.
“Optimism” in general is not necessarily the term we want to reclaim from the right: it’s wishy-washy, boring, mediocre. “I’m not going to do much, I’ll be on autopilot, because tech is good and it will sort stuff out. I don’t care too much about taking a position, beyond passively trusting tech”. Optimism is the happy trust of a dog on a leash going for a walk.
The core difference between longtermism and solarpunk is that longtermism stems from an utilitarian frame, while solarpunk rejects it. Radical utilitarianism like longtermist fashos and oligarchs gives them a way out to commit the worst crimes against humanity because of a supposed good that will materialize in a distant future. It’s a moral free pass, exploiting the life of future humans (who cannot protest) to justify the oppression and exploitation of current humans (who are indeed protesting these assholes).
Solarpunk and longtermism are in no way on the same spectrum.