Agreed, a 1080p or 1440p screen with good pixel-sharp graphics (which Mac OS does not provide, leaving you with blurry anti-aliasing) is all you need. 4K resolution is overkill.
the 1440p screen on my macbook looks incredible on macOS. Apple has been on top of the font rendering game for a long time now
Because you use a 1st party screen. It's like saying "Linux doesn't have any problems, look at my Pixel phone". Try multiple 3rd-party ones that aren't recommended by Apple and you'll see where the problem lies.