Reading and writing text is perfectly fine on a full-hd display if you have subpixel antialiasing. The only platform where 4k is barely enough is macos since they deliberately decided to remove subpixel hinting when they introduced hidpi displays.
I go blind when I look at a lower ppi display at this point. With or without subpixel AA. Weird how you get used to something.
Or just disable antialiasing altogether. Generally you'll want to enable full hinting too. Quality depends on the font. I use the DejaVu fonts because they look good like this. I'd actually prefer bitmap fonts everywhere, but this is almost as good.