Why do you think most websites today come with a "this website uses cookies" agreement at the top or bottom of the screen even before you sign up? By pressing "I agree", one could say you're saying you agree. You might argue "but I didn't sign up for the website", but it's not like someone out there can gatekeep what is considered "signing up". A TOS in any form is a contract, and what goes on within a website is up to its creators who made it. To use another semi-analogy, you might notice a certain place has a video camera recording its surroundings, and you might say it's wrong they think they can record you willy-nilly, although on the other hand, if you know it's there, it can also be asked what you're doing there if you don't want to be recorded.
I'm not a troll, I just know enough to respect when people running a website want to use their rightful authority as its owners to gather information, at least on a moral basis, versus when it is on an immoral basis, which would be if it's deceptive.
A website (at least those that end in dot com) are private property. It would be like recording footage of someone in your own home. All you need for that is basic transparency.
I am talking about both legality and morality, but they both refer to different aspects of all of this. For my case, I go by morality, but that doesn't mean certain aspects are necessarily illegal either. Selling info to a third party isn't a necessary part of the equation and not a part of what I was saying when I implied "as long as it's not deceptive".