Almost all commercial software are advertising their manufacturers other stuff. Ever installed a graphics card driver? How many ads does that show for games and software that can run on the card? Steam also pushes sales by pop-up advertisements.
Google has been fined multiple times because they went much further than just advertising their own stuff.
Can you disable ads on an ad platform with a single setting? Didn't think so.
So no, Windows 11 is not an ad platform, not even close.