The images above were not the most cases in real world. Most times when you scale down the tiny vector icons they might look really blurry so under some circumstances it's necessary to make pixel-perfect for low-res screens.

We all know UI designer is different from UX designer, UI designer do have priority to decide which tasks to do first, so readability is important but depends on the priority.

And when you are designing UI or other graphic works, so you think it's a good thing to say, "please don't make a professional job because this okay job doesn't bother me" Try talk to the HR when your UI friend is looking for another job:)