If fonts in your Haiku virtual machine also look a bit crappy, this might help you.
It took me a bit of trying until I found a resolution that looks good. My MacBook Air has a 15" screen with native resolution of 2880 x 1864 pixels. The macOS defaults to 1710 x 1107 with nice scaling.
In UTM Haiku’s screen is always scaled up. This means the screen is scaled at least twice until I can see it. This can lead to quite ugly fonts. Setting Haiku’s screen to a high resolution made the fonts look fuzzier and disproportionate or far too tiny for me.
I set Haiku’s screen resolution to 1440 x 900. In Appearance font smoothing is set to subpixel hinting at medium. In UTM’s virtual machine settings, I changed -> Display → Upscaling to Linear.
For your screen a different resolution, upscaling, and font smoothing settings might work.