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.
Facebook has my age and home town, knows what many of my interests are via groups I'm in. I don't think it's wrong to say I have given them that information voluntarily and so long as they keep it on their servers only, I'm ok with them showing me a mountainbike ad because I'm a 40yo male who is in a mountainbiking facebook group.
I don't consent to them showing me an ad for a specific mountainbike that I placed in the shoppingbasket at cheap-mountanibikes dot com last week, and then abandoned there, and the reason they know is because the store has some kind of arrangement of any kind with facebook. That's the kind of thing I don't think I should even be allowed to consent to.
I’m asking why you think that it’s a net negative that you’re able to consent to that.