The whole point of their foray into adtech was to figure out a privacy-preserving way to do it that doesn't involve wholesale selling people's browsing history.

How is that fundamentally different than what Google's done with chrome and the topics API? If you don't trust Google's solution, why would you trust Mozilla's?

Because most people in this discussion don't know or care about the tech, just "ads bad" and "Google bad".

If it's already essentially paying for them then .... what is the difference if they get it via Google or directly?