What are you talking about? Windows has an incredible app library, competitive (some say better even) with desktop Linux. Both of which have an even larger and more complete app library than OSX (and arguably the iphone.)
Take that App Library and compare it to iOS and Android. Windows is missing so many apps that people want it’s not even a comparison. Before Microsoft killed windows mobile they were desperate to get developers to make more apps for their OS. So much so that they
1. Paid people 100-200k to port their iOS or Android app to it
2. Invested in tooling that can let windows phone run ios and android apps natively
Both failed and now they are investing in PWAs likely with the hopes of getting a bunch of devs to switch over. With the end goal being them rereleasing windows phone in a few years with rich PWA support.
Basically the lack of apps killed windows mobile and would be no different here
All it needs is something for calls and something for MMS. Every other "app" would just be a Windows application. Windows application developers would be developing apps for it, but continuing to do what they do.