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.
The very ability to provide that list previously required an expensive secret police; today it does not.
This is an extremely dangerous ability for anyone to have -- human rights (such as that to privacy) were won against oppression. They aren't optional, they're the system by which we prevent those previous eras from reoccurring.
This is why i'm suspicious of the being a meaningful sense of 'consent' here -- if enough people consent, then the tracking agency acquires a novel political power over everyone. This is why the infrastructure of tracking itself is a concern.
Keeping all of the data under one company umbrella is vulnerable, target for hackers, and easy target for governments.
Your post is not correct.
No regulator will find any proof of anything though, as regular employees will not have access to such crucial data. Regulators will also can be fooled by the maze of interfaces and servers.
There is also incentive for governments to "not see" any wrongdoings of the companies, if they profit from surveillance system.
Ad business is like Palantir in lord of the rings. You do know know who is watching on the other side.
All you have is some "vague" promise from corporations that your data are properly removed.