Theme change doesn't work/ only changes accent color

Hi,

Hope you guys can help me.
I would really like to have some simple dark theme similar to PopOS and Manjaro default.
I found some nice ones on DA, but when I try to use them, barely anything changes.

When I try to change the theme in windows, it only affects the accent color (and sometimes cursor and wallpaper, if they were included), but the visual style stays the same default one.

I'm using v2004, but it was like that on 1909 too.
I installed uxpatcher, and did everything else from this tutorial
Guide To Installing Windows 10 Themes by niivu on DeviantArt
I don't think I did anything wrong. I only tried themes that say are compatible with my version.

I only recently wanted to change w10 theme, but this isn't my first time changing themes on windows.
I never had this problem back on XP and 7.

It seems to be a software error, idk.
I replaced UltraUXTheme Patcher with the regular uxthemepatcher, that fixed it, finally..

Still, thanks you answering :)