Wallpaper Blur x Display Resolution Problem

Guys, I am having a problem.

I noticed one day that my MacOs Catalina & Big Sur wallpapers are a bit... pixelated, like kinda blurry, i didn't understand what's going on, they were official on system wallpapers, how could they be blurry, i asked around AIs, tried to tweak things and found out that my macbook's display is not running on it's native resolution, i.e., 2560 x 1664, but it was running on 1470 x 956, and this only was labeled as "default", but then why was 2560's option was even given in the first place if it's not default, i mean why give a higher resolution and not keep it defaul, so i clicked on the 2560, and my wallpaper turned crystal clear, sharpest ever, but everything else, the icons, the text, the windows got miniaturised, like they became 25% of their original size, barely readable, so i had to switch back to the default and my wallpaper got blurry again!!