> at the same time, desktop Linux distributions and macOS keep iterating and innovating without having that burden.
That's a bit of a re-write of history. Mac OS tried to throw away all backwards compatibly on day one but major software vendors told them to pound sand so they had to spend another year building out Carbon. Not to mention that Mac OS X itself is built on NextSTEP.
Linux breaks front-end compatibility so much that never seem to make much progress on stability.
> on top of that, technical baggage keeps holding back Microsoft as well. Apple ditched Intel long ago and now reaps the reward
It's not technical baggage that is the problem. It's strategic issue. Microsoft had a fully functional build of Windows 7 for ARM a long time ago. The problem is they never just released an ARM version of their OS and let developers port their code to it. It was always paired with a new API, the windows store, a locked down version of the OS, etc, etc. This might be specifically to avoid pissing off their hardware partners.
Windows NT was always multi-platform and they always made sure it would build and run on non-Intel CPUs. It has never been a technical issue.