Microsoft can no longer engineer a software product, it simply cannot build anything innovative. It can certainly buy other companies and use what they have built. But even then they will over time ruin the product.
If you put together an amazing team, in the same building, with the goal of getting Windows under control, then you would at least have a chance of succeeding. You would have a whole new set of problems though and that’s where you would need an amazing manager that had the final say on every decision. A trusted team that could be left alone to succeed.