I had this issue, then compiled emacs --with-pgtk
and fonts became way better.
However, recently, wsl2 was updated in my win11 and out of curiosity I had recompiled emacs without pgtk and fonts are actually crisp and look the same as --with-pgtk
.
I am staying with X due to better clipboard support, though, ugly white borders are something you have to "embrace" :)