Technically they are not preventing you from working on it, they are just not making it easy by open sourcing it. Personally, I would like to modify my OS and contribute the changes under a liberal license such as MIT but the terms of GPL can make it tricky. However it will be wrong of me to go around demanding older phased out Linux distros to be re-licensed under a more liberal license.
You won't be able to distribute your fixes (because they contain MSFT copyright protected code), reverse engineering the binaries and even the API might be a violation of the DMCA, and you will not be able to update system files from within the system it self.
So yes they kinda preventing you from working on it, at least for the benefit of anyone besides your own intellectual curiosity.
That said I don't see any problem with MSFT dropping support for XP, they supported it much longer than any software by any vendor closed or open sourced.
GL getting support for RHEL 10 years down the line if you haven't upgraded your OS, and Linux from 10-15 years ago has as much in common with Linux today as Windows XP has with Windows 10.
> Technically they are not preventing you from working on it, they are just not making it easy by open sourcing it.
Technically, they are preventing you from legally doing most work on it, since (in the US, at least) creating (not just distributing) a derivative work is an exclusive right under copyright for which they do not license you.
Not that I agree, but the FSF's issue with non-free software does not seem to be purely based on those who sell proprietary software lying (or being unclear) about the limitations, but at least partially on the fact that they even offer such "raw deals" to begin with.
Given that Microsoft has long published the support lifecycles for its major products, and that those support lifecycles are often guaranteed (as much as anything in the commercial world can be) many years into the future, any criticism on this score just feels like bad faith.
The alternative is to take your chances with free software where outside of any commercial support agreement with a specific provider you generally have no actionable guarantees of any kind that your support will last as far as the time your installation completes.
Yes, you're right, in the end is the users fault as they didn't foresee those consequences and some didn't even made migration plans, even when stated clearly.
You can even argue that all of the things there end up being the users fault as they choose so for convenience.