You're asking developers at the largest ad company in the world why some of the development they do relates to ads. It has nothing to do with engineers vs managers, both are and have been willing to push against user interest for the vast piles of money.
I can't tell if this is a serious question, or just some quip. Assuming it's serious...
It's not an average SWE's job to make product decisions and to steer strategic initiatives. There are people whose job it is to do specifically that.
Think just for a second what it would be like if every one of be more than 100,000 employees could bring a product plan to a halt because they had reservations.
What's in your power is to ask tough questions (people do)..
To make your opinion heard (people do). To change projects if you wish (something Google makes easier than any other company). And to take risks and make choices in the execution of your own job duties. That's psychological safety.
You may find this hard to believe, but the people working on FLoC have chosen to. They could easily find a different project if they wanted to. It may be disappointing you you that the average SWE isn't nearly as ideological as the average HN commenter, but it is what it is.