show me a screenshot of your assettocorsa folder, reinstall is almost definitely unecessary, instead you can do as i said above deleting all the files in the root (check for hidden too) and do the steam integrity check to restore only the official files.I think i must delete whole game and install again...
there must be some other files there from another sweetfx or similar. look for stuff like efx, dxgi etc. check there arent any sweetfx files in the MODS folder too, but pretty sure the game wont detect those, will check back tomorrow morning