We are absolutely sleepwalking into the worst possible tech futures. It's so ubiquitous now that even if you're able to explain to someone how bad things are, trying to avoid this type of data collection would almost take Edward Snowden - level planning and obsession, so people just kind of give up before they even start.

The truth is that even the small actions you can take help make your data a little less valuable. They're collecting so much data from so many people, that they really don't have any easy way of verifying the data in your profile. So while there's essentially no way to go back to when you had NO data, the accuracy and relevance of the data can be soured so that their use-cases for it are less successful. Assuming you're already using an adblock or VPN to do most of your browsing, the biggest things are phone app data collection and purchases through a credit card via online portals as well as in-person. If you can avoid those, most of what they use the data for is a lot less successful. I would also avoid social media apps or sites where login is required, as they can scrape data on how long you look at any given image or ad with a pretty high degree of accuracy.

If you're dead-set on perfection, you're bound to feel helpless. But you should feel good about the little steps you take that 80-90% of people aren't, because you're that much harder to target via your data footprint.