In most, but not all installs, the start menu pre-installs game ads, explorer advertises for onedrive, and the lock screen advertises things on top of the pretty pictures.
But.. I still get winrot, and my dev environment drives me mad. I've been working on a laptop since covid started, and my dev machine is a VM on the laptop, so it's a nightmare.
At home I run NixOS with a Win10 VFIO setup for games. Both Linux and Windows at home are drama-free, but I don't abuse my home computer nearly as much and it's much more powerful than the work laptop.
And people really need to stop expecting that paid products won't show ads. From the POV of the provider, not showing ads would mean leaving money on the table (you likely won't quit paying over just an ad here or there). On top of that, as a paid customer, you self-identify as a real person with disposable income, making yourself much more valuable a target for advertisers.