In Settings > System > Advanced System Settings > Advanced tab > Performance > Settings > Visual Effects, Windows 11 always changes the check boxes to what it wants.
This is what I want ...
And this is what Windows wants ...
Windows will maintain my choices until I sign out of my user account. The next time I sign in, Windows has replaced my choices with its choices. This is infuriating.
How can I get Windows to leave my Visual Effects choices alone?
I assume you're remembering to click Apply and OK, when you choose your settings?
If you're clicking Apply and OK, and they are still changing... open a command prompt as Admin and run these two commands, one at a time...
sfc /scannow
Dism /Online /Cleanup-Image /RestoreHealth
If they come up clean... and the problem still occurs... then maybe you're running some 3rd party tweaker and have set some things that are over-riding the Visual Effects settings?
Or maybe you chose a "theme" in Window's settings, that is over-riding the Visual Effects settings.
Windows 11 is still somewhere between the old Control Panels and the new Settings app. Settings that you make in one place can be overridden by settings that you make in the other. I had to go through the Settings app very carefully (including Accessibility settings) to turn off visual effects that I did not want. (Hat tip to Paul Thurrott.)