MAUI was promising to become such a thing [although MS themselves are being a bit non-committal about Linux], but should I be wary of the bigger architectural picture?
.NET has long been rock solid in C/C++ <=> .NET transitions and WinRT <=> .NET transitions. (System.Windows.Forms does a ton of it and .NET 5 seems to have the expected performance from all those transitions.) The new interesting transition that it is still too early days to tell how well it will perform is the new .NET approach to Objective-C <=> .NET transitions/projections (which is more like the modern WinRT projection techniques) that is also different from the Objective-C <=> Mono transitions in Xamarin.Forms. (Though the article points out that the Objective-C <=> Mono transitions were fine and the new .NET approach on paper should be even better.)
Also, from what I was reading, a modest version of the architecture change that the article was lamenting needed to happen to reduce Java <=> Mono transitions in Xamarin.Forms is supposedly happening in MAUI and they were trying to reduce the surface of "managed Renderer" code that transitioned in/out of OS level services. I don't know if what they are doing would be enough to satisfy the article's writer, but it apparently has been something on their radar.
You shouldn't be wary realistically because Microsoft has spent almost a decade grinding away at something that needs to exist for both Windows to survive, and for Microsoft to stay relevant in app design. The existing code that makes WinForms, WPF, and WinUI 2 apps (the API in UWP) also has been reused or extended by WinUI 3.
Microsoft just wants app development not to suck. They designed C# for a post-Java world for this goal, they rebooted Visual Studio years ago for the C# era to achieve this goal, they took XML out of the places it didn't belong and put it into the places it did belong (ex: XAML, for actual real document-style code autogeneration) for this goal, they switched to Git to handle their famous monorepo to accelerate development of Windows, they bought Github because of how much they used it internally (and made their job so much easier than their kinda shitty internal mixed heritage VSS quasi-fork), and they're one of the largest users and committers of the Linux kernel itself and would love if they could run their own modern MDL2/Fluent(=MDL3) apps on Linux natively.