25 years ago
There was some tech stuff, new-deal-with-chinese-characteristics, and specifically a very climate conscious US president was elected, but everyone just let the other guy take office.
climate activists stopped nuclear
No. Dipshit appropriate environmental and residual anti nuclear activists, which were tangled up wuth a bunch of other movements, stopped it. Wouldve been nice though.
only technological solutions
I think i said 'no changes (that wouldnt have improved our quality of life anyway)', so things like modal shifts in transportation and moving to dense walkable cities or well cared for and/or utilized rural places
Things like solar and wind power (and yes nuclear, especially back then)
starting 50 years ago
Bitch have you not heard of jimmy fucking carter? Do you not remember the solar panels on the white house? Dude wasn't perfect, but he proposed both renewables and nuclear power, and i assume knew what the hell he was talking about (given his education). It would have taken some time, but if we had started then, i think we'd be in a pretty good place. I dont know much about the situation on the periphery, but i assume the USSR would have matched the americans if only for the sake of appearances.
whataboutism, absurd bullshit
Okay you dont seem like a serious person; i wish you luck at the fracktory.