Assassin's Creed Games Totally Screwed on PC

Other than Ubisoft being Ubisoft, why are PC ports of their most recent titles in such a shoddy state?

Re-downloaded AC Shadows and apparently there's an issue with a Windows update that is literally halving the FPS. Second time it's happened too

Said ok, not going to do with that, so I re-installed Valhalla. Played for a few hours just fine but now I am crashing every 10 minutes.

I also played Unity (how recent is recent), and had to limit the FPS to 120 because the FPS would outrun the game's ability to render the environment.