Quite the opposite. I see it as a reason *to* use one account. I don't pine for the experience of every device being different, nothing synced, using networks or USB to get files from one device to another. I expect to shutdown my desktop, continue working on my laptop, and be able to see the results on my phone. It's 2024 not 2004.
Maybe the cloud isn't for you, but the feature set provided by synchronised experiences are real features that people go out and actively seek.
OneDrive is still optional and worthy of a global boycott
Why? That's a big statement to make. Justify what makes it worthy of a global boycott.
Don't purchase shit from a Microsoft Account
So ... break many current multimedia apps? Virtually everyone needs to purchase at least one thing from the Microsoft store. Windows doesn't include a native HEVC decoder which some 3rd party apps rely on. It's only 99c sure, but it's objectively a purchase worth making. That is a real "no-brainer". Again you say don't do something without telling us "why". Why should we not purchase from one specific store you you don't like. You're calling for a boycott again without justification.
Use a separate account for each and every computer (a no brainer)
So break device synchronisation between devices. Why again? What *benefit* do I gain when I weigh that against the loss of features?
The snag are the people who insist on sharing all their files with all their devices, maybe they feel like they have to take the job work and do it on their home devices as well while sitting on the toilet?
My devices are my devices. They aren't job / work. They are personal / personal. There's more than one place to sit and relax at home. Maybe I'm working on something personal on my desktop and the weather gets nice outside, so I'll grab my laptop or tablet and continue in the hammock. While there I come across a recipe which I save as PDF for later (I have a huge cooking library these days), but I don't cook with my laptop (disgusting), which is why it's great that I have my cloud files available on my tablet. Not everyone fits yours twisted view of working on the toilet.
Basic security would imply not to use a single point-of-failure password for *everything*.
Funny, Microsoft thought of this too. Which is why a Microsoft login is rarely used for anything other than a backup when primary authentication and tokens fail and for a single setup. That is the fundamental point of Windows Hello. - Authentication without having to type your password in where it would need to be sent over network, or visible to someone looking over your shoulder. And it's also the reason why Windows will ask you to setup a separate Windows Hello authentication for you device immediately after logging in (or creating) a Microsoft account. All my devices login via pin, and my pin is just as complex as my normal password, and each pin is different. You're not smarter than a Microsoft engineer, even though you're on Slashdot so you most definitely think you are.