Ads and personalized ads are two very different things. Duckduckgo works fine on the former.

Personalized ads put you into an information buble, collect your personal data and manipulate you into buying what you don't need, harming you and the environment. See also: https://www.socialcooling.com/.

Also, what Facebook is doing is beyond unethical: https://news.ycombinator.com/item?id=24579498.