In case anyone else has been low-key bothered by the fact their Excel formula bar seems to have turned into a strange monospace font — you can change the default font around & that impacts the formula bar. Arial looks fairly reasonable for me. But there are lots of other fonts to chose from!

Also looks like a future update will include an option to not use monospace fonts for formulae … https://techcommunity.microsoft.com/blog/excelblog/excel’s-formula-bar-gets-a-new-look/3902462