But despite that, as a Windows user I acknowledge that any kind of interaction with another Mac from within MacOS (Handoff, Sidecar, Universal Control, Bluetooth-pairing to Apple-ID instead of Hardware MAC-ID,...) is leaps ahead of what Microsoft was doing with their OS for the past years.

Just the scenario of an employee getting a Windows laptop as a work-PC, there's barely any halo-effect if he/she also uses Windows at home. No easier handoff, no interaction, hardly any "just-works" connectivity.

Windows is mostly a vessel for the (legacy) applications it can run, and for these Browser-based Microsoft Online-Applications (which work equally-well on other platforms)

They didn't invest in creating "just works" frameworks for their PCs which amplify the ecosystem the more compatible devices you have, instead most of their focus is now on "just-works" stuff in the cloud.

So if Microsoft would make a clean cut on backwards-compatibility, I'm not sure there would be a reason left for most B2C users to even stay with Windows.

The "you can make it work if you invest a bit of time or google it" paradigm is nowadays well-covered by Linux already, and it's getting even harder for brands to compete on price/quality with Apple's scale, for almost any portable device...