So what exactly are we complaining about here?
I don't mind having an MS account, I've had one for years. I have almost never used it for anything. I'm not interested in the advantages of being logged in with it. My general practice, with very few exceptions, is that I don't stay logged in to anything unless I have a reason to be.
I really don't mind (too much) that they've decided to nudge me to log in with that account. I do mind that they haven't just provided with a straightforward means to say "No, thank you" and be done with it.
I'll admit that I do have to wonder why they spent the money on creating the nudge, and why they seem to have intentionally ignored the choice to opt out. Companies usually don't spend a dime on anything unless they expect to get more back one way or another.
As for Mac, iPhone, iPad, Android - not my problem.