There’s a great article with explanations on the net. But the gist is that macOS renders like a giant image with no care for pixels and small details. It works fine when using native resolution (low dpi) or have enough pixels for their “retina” approved resolution. Anything else and it looks blurry.

Linux and Windows use actual pixels for their rendering, and even with anti-aliasing, it looks sharp. If you’re stuck with macOS, aim for 4k at least.