We probably get used to whatever font rendering the systems we use the most have.

To me, fonts indeed look blurry on macOS and weird on Windows. Screenshots from Windows with colored pixels particularly don't look good to me. Though after having seen screens of people using Windows 10, it seems they changed whatever I really didn't like about font rendering on Windows.

I still like font rendering on GNU/Linux (and Android) better it is correctly configured, which it is on widespread distributions with widespread desktop environments (I use a QHD screen). But it could be out of habit. On some configurations, kerning is bad though.

Perhaps the screenshots you're seeing have ClearType (i.e. sub-pixel anti-aliasing) turned on, and when it got to you (as a picture) the subpixels no longer match on your screen? For example, if one of the screens involved was vertically oriented…

This is it. This was more of an aside, it's indeed not supposed to look this way when it's directly rendered on the screen.