You're either commenting on something you are oblivious about, or are pulling a red herring just to be contrarian.
Concepts like revealed preferences [1] are nearly a century old, not to mention the fact that the whole consumer behavior field as a whole has plenty of quantitative methods to infer "what people like".
Facebook and Twitter support a feature where quite literally users specify in no ambiguous term that they like something. Theirnl platform is so effective that their problem is filtering out bad actors.
Then there's also engagement. You can get a pretty good idea of what people are interested in by tracking what they read.
You might try to nitpick about the true meaning of "like" but you'd need to be really determined to intentionally miss the point.