Personalised ads are beside the point. The issue is how they are personalised, namely by building a rich profile of user behaviour based on non-consensual tracking.
It isnt even clear that there's a meaningful sense of 'consent' to what modern ad companies (ie., google, facebook, amazon, increasingly microsoft, etc.) do. There is both an individual harm, but a massive collective arm, to the infrastructure of behavioural tracking that has been built by these companies.
This infrastructure should be, largely, illegal. The technology to end any form of privacy is presently deployed only for ads, but should not be deployed anywhere at all.
Will the EU fix Windows by banning the insane amount of tracking they do? Would be nice. The OS is literally at its peak in terms of being great, but all the telemetry, forced accounts and Microsoft ads keep the meme alive that Windows is awful, when in fact, if you remove those three things I mentioned, you have an insanely reliable and polished OS, all my issues with Windows have always come from customizing the core OS, it just doesn't quite behave the same, I would eventually format due to issues, the moment I stopped tampering and tinkering, I've stopped reformatting Windows.
But that's about it. For regular users, Windows 7 has been the best, and after noticing how my parents struggled with the updates, nothing can convince me to think otherwise.