I've seen a few #SciFi stories involving timelines that split off several millennia back. They generally follow the Twilight Zone style of ending - effectively, "Well, *that* MC's screwed."
I've also seen too many alternate history stories where even a big change doesn't produce major divergences. Things are still mostly familiar.
Then I heard about Naomi Alderman's THE POWER and saw a way to avert those tropes *hard.*