I had a 34" 4K monitor in 2019, and it was a mess in Windows 10. I sold it and picked up an ultra-wide, 38" 3840x1600 (~109 PPI) and I couldn't be happier. I agree that a "good" monitor is a necessity, but I disagree with OP that "good" = 4K 120 Hz.
With any legacy application, and even many modern ones, UIs were either fuzzy, or tiny, or a mix of the two, even with all of the Windows per-program custom high-DPI settings tweaked. The UX was not consistent enough to be enjoyable, so I ditched it.
For what it’s worth, the “fuzzy” version is usually about what you’d be getting on a display if it wasn’t HiDPI. Also don’t forget to exclude the rarer, but still happens scenario where the UI is scaled twice for some reason, so everything is huge.
With any legacy application, and even many modern ones, UIs were either fuzzy, or tiny, or a mix of the two, even with all of the Windows per-program custom high-DPI settings tweaked. The UX was not consistent enough to be enjoyable, so I ditched it.