I always hear people complain about this. I never see it. I use Windows 11 and I never see any ads. The closest I get to is if I search and bing pops up, but that's it. I also turned off all the extra crap, my taskbar and search menu are as bare-bones as possible.
Edit: To clarify, I run Windows 11 Home.
Its not a thing on windows 11 pro, only home it seams.
Yeah - a fresh windows 11 home install is pretty aggressive. But if you use the pro version or run a cleanup script it’s not bad.