"Sell with efficiency" sounds a bit vampiric to me; a bit growth-at-all-costs or refusing to accept the normal costs of doing business (although I can sympathise with that mindset).
Where do you draw the line? This is parallel to the discussion around government surveillance. Just be cause they / you can, doesn't mean they / you should.
If Internet tracking had no potential use to governments then they'd be regulating the shit out of it. The problem is that governments want their own noses in the same trough, and so all these privacy-invasive technologies continue to be developed. The fact that it's not illegal means that anyone with the ability to implement it can, as long as they can sleep at night.
As to solutions that could help with "selling efficiency", maybe some kind of agreed tiers of analytics from benign to spooky that users can opt-in / opt-out of when visiting a website or using an app. Which GDPR is a bit of a kludgy solution for. The problem is that it only takes one bad advertiser to break agreed rules and the trust is gone again for all advertisers.
One bad apple.
Analytics are unquestionably useful. Collecting the data without user consent is what potentially should be regulated.