If product is free then you are the product. And targeted add serving is not the worst case. It is proven that those holding your personal data to a great extent can and do manipulate your behavior over the long term. Fuck those platforms. Even though they are a perfect way for businesses to promote themselves, they do not provide any value at all for an average user. Nothing, nada.. at all.

I suggest watching "The Social Dilemma" for a information that actually just scratches the surface but provides pretty good general understanding how the system works.