I honestly don't envy Microsoft. On one hand, you have the people who don't want Microsoft to break backwards compatibility. They want Microsoft to retain the ability to run programs written a quarter of a century[1] ago. This is why all this legacy stuff sticks around in Windows. Then, you have those who want Microsoft to radically reinvent Windows, either by embracing WinUI 3 fully (what most people mean when they say UWP) or through something even newer. Windows 10X was a sort of middle ground: a OS that pushed all the old cruft into isolated containers. Sadly it looks like that approach isn't going anywhere (unless we see it come back in Windows 11). Project Reunion is a nice attempt to give developers an incremental upgrade path to modern Windows, so I'm hopeful that within the lifecycle of Windows 11 we'll start to see Microsoft develop a reasonable separation between modern and classic Windows apps.
[1] Edit: quarter of a century, not quarter of a decade.
[1] Edit: quarter of a century, not quarter of a decade.