I don’t get it how the game ends at step 18. How about rendering the page in a headless browser in the background and then cut out the ads. We could also use heuristics to filter out ads. The authors argue that the ad-tech industry could have dominant access over the DOM but that’s never the case, quite the opposite. The user has dominant access because he’s the one executing the damn thing.

They don't seem to understand the lifecycle of page rendering. They assume some strange situation where the server maintains state forever and thus has permanent access to the DOM. That's hardly how the web works. Once the page renders it's game over for any kind of ad-tech. We own the DOM. Period.