Not really slower, just more shit going on under the hood than ever before. Considering all of the novel ways to attack the operating system, the ubiquity and level of integration of computing in everything, the OS is a much higher value target than it used to be back in the days of Xp-7. However, MS has introduced numerous security features and significantly improved the built in AV. 10/11 is a hell of a lot more secure, but there is a performance cost to that. That and the software we run on top of it has only gotten more resource hungry and complex as well. There are also things that you might hate but are worlds better than they used to be. Updates are a lot faster, support automatic rollback and are practically flawless compared to the broken mess they used to be. We now have things that were never possible before, like first party tools to convert a MBR/BIOS-boot system to UEFI boot.

I'll concede the point about service advertisements, however depending on the edition that is suppressable. MS is not alone in its sinful capitalism however, MacOS is full of stuff like that too, they're just sneakier/more subtle about it. MS will have you griping about their promoted services or apps; Apple will have you licking their boots and not realizing it because you've deluded yourself. The only operating systems that are really free are the ones no company fully owns. I work with multiple different operating systems in an IT job, and the notion that it is acceptable to run old versions of Windows in this day and age or that they were objectively better is just nostalgic horseshit. It was always a corporate product, you're just chafing against that now.