If my file manager or desktop utils don't open in less than 50 milliseconds I won't use that DE.

You can even test this on linux with the time command.

XFCE is just simply the best desktop. It's 30-40 milliseconds on average for every app and switching between tabs/folders is instant, thunar is amazing. Most apps on XFCE run smooth, alttab is fast and snappy and XFCE has so much customization like shortcuts that are extensive with keys and tiling. I can never go back to windows.