Nobody is saying that they shouldn't be able to, rather that they should be informed as to what they're doing so they can actually make that decision. Without knowing what is happening, they cannot make an informed decision.
Facebook and Google should get in major trouble when they mistreat their data (like the Cambridge Analytica scandal with Facebook), but you disliking the data they collect and/or their business model does not mean that everyone else will.
I know full well the type of data Google and Facebook collect about me and I just don't care. There's plenty of people in the tech industry that don't care either.
I never said that, in fact I explicitly said the opposite.
"I know full well the type of data Google and Facebook collect about me and I just don't care."
Yes, and you were able to make an informed decision because you do know. Not everyone knows. That's the entire point I was making.
> that they should be informed as to what they're doing so they can actually make that decision
These two items are at odds with one another in an opt-in situation.