I’m not sure how it would all work out. But let’s start where we are now with search engines.
Remove the ads and make people pay to use them beyond some number of queries a month. This alone gets rid of the problem of the platform intentionally shoving ads down your throat.
Find a shitty website that SEO’d it’s way to the top and got through the cat and mouse game? Then allow people to blacklist websites so they stop appearing in results. Then as the provider investigate and downrank sites that people downrank and block often.
Maybe also preferentially treat companies that don’t load their own sites with other people’s ads and tracking scripts. Oh and tell the user how many of those trackers exist on the site.
This obviously don’t solve the problem of companies pushing ads onto you. But it:
1. Sets up your information provider to not be the biggest and worse ad pusher of them all.
2. It gives people the tools to start penalizing bad content and ads and to outright block them from their results.
This alone, I strongly believe, would be a great improvement.