To be fair, improving performance on Windows is not really a priority for GNU. From the GNU downloads page for emacs (https://www.gnu.org/software/emacs/download.html#nonfree):

> To improve the use of proprietary systems is a misguided goal. Our aim, rather, is to eliminate them. We include support for some proprietary systems in GNU Emacs in the hope that running Emacs on them will give users a taste of freedom and thus lead them to free themselves.