That's fine and been going on for hundreds of years.
It's the underhand, illicit collection of personal data and personal usage of the Internet that's wrong.
Billboards, Radio, TV, Magazines and newspapers manage without that. Does it even work very well, or just fake snake oil to get the advertisers spend with Google, Facebook, Amazon et al rather than the other outlets?
Adverts are legal. Snaffling people's personal activity isn't, even before GDPR.