It turns evil in the presence of corruption. Taking bribes in exchange for power. Government should never make rules for money, but for the good of the people. And advertising should never offer exposure for sale - exposure should only result from merit.
Build an advertising system with integrity - in which truthful and useful ads are not just a minimum requirement but an honest aspiration and the only way to the top of the heap. Build an advertising system focused, not on exploiting the viewer, but on serving them - connecting them with goods and services and ideas and people and experiences that are wanted and that promote their health and thriving.
I won't work on advertising as it's currently understood... I agree it's evil. But I'd work on that, and I think it would be a great good.
AI has the potential to go in many directions, at least some of which could be societally 'good'.
Advertising is, has always been, and likely always will be, societally 'bad'.
This differentiation, if nothing else.
(Yes, my opinion on advertising is militantly one sided. I'm unlikely to be convinced otherwise, but happy for, and will read, contrary commentary).