WinRT is not the same thing as managed .NET code. There is no requirement that a UWP is .NET. There are many examples of unmanaged C++ UWPs, including the open source Windows Terminal.
WinRT is a mechanism to express APIs in a way that is amenable to cross-language usage. It is built on top of COM, and is not a replacement for COM.
WinRT is a mechanism to express APIs in a way that is amenable to cross-language usage. It is built on top of COM, and is not a replacement for COM.