Adtech is a pretty big bubble. Failure would be disruptive. But from a long-term perspective I'm not convinced adtech is desirable or needed. Let's go to Luna and the icy moons instead.
As long as people who have next to nothing (a large portion of the world) can access valuable resources for free in exchange for looking at advertising, it is quite necessary. Even those who do have disposable income in first world countries are not interested in paying for a subscription to resources they rely on a daily basis. Ads are a necessary evil.