For the main menu i try to make them as heavy as the main game so people know what they are getting in to, and yepp, that explains the motion blur, idk, game is heavy, unity HDRP :).
I can look in to graphics settings like shadow distance and general quality option, i always try to target 100fps as minimum for my pc but ye a lot of people have lower pcs and i don't know how much is possible. (i use Unity's HDRP pipeline which is their heavy "AAA" thing that they are neglecting)
For my next game i will try to include more options but the game will be heavier (no low res option but it will have FSR3).