MacBook Pro 2012 Catalina dark mode problem

Hi,

I cant get the dark mode work properly on my MacBook Pro. As you can see on the screenshot below, when switching the appearance to Dark, all that happens is, that the top menubar turns to black background, but everything else stays the same as in the Light mode.

I set up a new user account on my Macbook, and logged into this new user the Dark mode works as it should, every window/menus/dropdowns have black background. Therefore it seems that there is something with my user settings, that breaks the dark mode in my account.

So I made a clean install of Catalina, recovered my documents and files only with Migration assistant, and it seemed to work (dark mode worked as it should), but the I got an 10.15.7 security update notification, so I installed it, and once the Osx restarted, the dark mode was broken again, same as the screenshot below.

Any idea how to solve this? Your help would be appreciated.