Why did fonts go so wrong in Windows? [closed]

Microsoft have done a series of efforts to make the fonts look better on different screens. For instance, Microsoft invented ClearType, which was absolutely breathtaking back in 2000, and they created custom fonts such as Segoe UI which also—back then—looked like an excellent alternative to the existing fonts. I remember, a long time ago, that the default rendering in Windows looked much, much nicer than the custom one in Adobe Photoshop (running on Windows), which was always muddy/blurry/weird.

Despite their efforts, it doesn't seem that they are doing great compared to the competition:

  1. I maintain a website where I take great care about how things look, which includes anything related to text: fonts, sizes, spacing, text rendering. As I work on Linux, I'm always surprised how the site looks ugly on Windows. It should be the same font (from Google Fonts), but at pixel level, it just doesn't look right. Aside, Unicode characters get smashed, spacing is changed, etc. What a mess.

  2. Recently, Stack Overflow announced that the custom fonts will be replaced by the default system ones. I wasn't at all optimistic about the change before they did the switch, but one morning, when I discovered the new version, it looked actually better than the original. More readable on Linux at least. On Android, I don't see much of a difference (maybe because I don't use the site as much on a smartphone). Similarly, a colleague who uses an Apple computer found that the site looks much better now.

    To my surprise, the announcement received plenty of negative comments:

    • “The fonts look truly horrific.”
    • “Oh my eyes... this font seems pixelized.”
    • “Ewww (Windows 10). Can we have the old ones back please?”
    • “Code fonts look blown out (font-weight) and fuzzy at the edges.”
    • “As a nearly 50 year old viewing the site on Windows 10, this change is terrible for my aging eyes.”

    The comments go on, and so do the upvotes of those comments. Although some don't tell what OS are they using, many do confirm that they are Windows users.

I would expect—exactly as Stack Overflow designers expected—that the default OS font should be highly optimized, properly configured for a given device. It seems that this is the case for Apple, Linux, and Android, but absolutely not the case for Windows.

How did it go so wrong for Microsoft?