Not everyone can just "choose" what field they want to be in. If I got to choose what I did every day, I'd be a writer or a musician. No ethical concerns there.
You don't have to work in ads or tracking technologies. Unless you are quite junior and needed to accept whoever was willing to take you. But based on your knowledge of the industry it seems you've spent quite a bit of time there.
Most people who work for eg google s engineers have plenty of other decent paying options, especially right now. Sure, not everyone diodes, but most do.