Btw abour Aeldari, it’s very likely that Emperor sabotaged them.

Their civilization lasted for 60 million years which means incredible stability not known to any other species including Necrons and possibly even the Old Ones. But they fell only in last 10-15k, which even for their personal lifespans seem very abrupt. There is also confirmed in lore there was no outright hostility between humans and Eldar (they allowed humans to spread and traded) before their fall, which means that decadence was grossly overstated - their entire civililization just couldn’t be at the level of of current Drukhari as it is claimed many times (iirc the source of those claims seems to be Asdrubael Vect who is worst possible source on this).

It’s basically confirmed that Emperor greatly feared the Eldar since he might be most powerful psyker in the galaxy, but Eldar had probably billions of beta class psykers and above. Also he only came out of the closet after Eldar empire was truly confirmed destroyed, the exact date is incredibly suspicious. Most of canon books place the fall of Eldar as a process that ended or even happened up to literal begining of the reunification of Earth, which means Emps waited exactly as long as it was necessary for Eldar to stop being a danger to him and then abruptly moved in a blitz.

All that is way too coincidental, it’s also very fitting with all the other cases where Emperor actions ended up empowering chaos.