I’m sure there are many ways to do a restyling, similar to the Apple Aqua UI [0] for example, that could create a fresh look, while maintaining the clear affordances.

[0] https://en.wikipedia.org/wiki/Aqua_(user_interface)

The issue, I suspect, is that the young UI graphic designers working at Microsoft today mostly didn’t grow up using PCs and therefore don’t really know what their missing.