> So what are potential solutions?
It won't fully solve the problem, but with the problem relatively identified, you must then ask why people are engaging in this behavior. Answer: money, for the most part. Therefore, follow the money and identify the financial incentives driving this behavior. This leads you pretty quickly to a solution most people would reject out-of-hand: turn off the financial incentive that is driving the enshittification of the web. Which is to say, kill the ad-economy.
Or at least better regulate it while also levying punitive damages that are significant enough to both disuade bad-actors and encourage entities to view data-breaches (or the potential therein) and "leakage[0]" as something that should actually be effectively secured against. Afterall, there are some upsides to the ad-economy that, without it, would present some hard challenges (eg, how many people are willing to pay for search? what happens to the vibrant sphere of creators of all stripes that are incentivized by the ad-economy? etc).
Personally, I can't imagine this would actually happen. Pushback from monied interests aside, most people have given up on the idea of data-privacy or personal-ownership of their data, if they ever even cared in the first place. So, in the absence of willing to do do something about the incentive for this maligned behavior, we're left with few good options.
0: https://news.ycombinator.com/item?id=43716704 (see comments on all the various ways people's data is being leaked/leached/tracked/etc)