I disagree. I think UWP has done a really good job technically behind the scenes, but poorly explained publicly of showing how one device's display and input device constraints are another device's accessibility/ease of use guidelines. That the basic "common denominator" made things easier/better to use in general for everyone, even if users/devices were capable of fewer constraints and more guideline breaking.

In addition, UWP and Fluent Design System had a hard time coming back from "these are the constraints in all situations" to "here's how you flex when these are the constraints of the current system versus when they are merely guidelines that you can break if your user accepts it". That became a focus in Fluent Design System 2.0, but it certainly does feel like it may have been too late avoid the "worst common denominator" branding that Fluent and UWP got painted with early on.

UWP/Fluent did a lot of things right technically that Apple should apply to efforts like Marzipan, they just might not realize it based on the tarnished brand.