That could be an interesting setting.

War of Theseus.

Vaguely reminds me of a backstory for a stardrifter campaign I homebrewed. (My universe, stardrifter rules.)

Basically, earth history was that scienctists and academic types fled in the first Terran exodus. These became super advanced, called “solarians” though eventually also splitting offshoots on other worlds all of which were connected by jump portal (basically star gates in function but they moved a sphere one way, rather than a gate you walk through)

The second group were zealots that stayed behind becoming dumber and regressing, surviving a nuclear winter, until getting out to the stars and meeting the solarians, whose tech they steal but never actually understand. Arcana being the religion they follow literally using solarians tech as magic.

Shitnhappens back on earth driving humans away and wiping all life. from it as a galactic civil war happens across a few eons or so.

Eventually, a new humanoid-ish race evolves again that was in the middle of their Bronze Age when some solarians exiled come back and introduce religion in the hopes of creating super soldiers.

Things change and the setting of the actual campaign is analogous to contemporary technology…. When Stellarian assholes show up preaching the good word Arcana