you can still leave a shitty comment, its just your negative feedback in the binary only goes to the publisher to show them that they have missed the mark as opposed to signalling behaviour to others (still possible with comments).
The social signal that a large number of people disapprove of content is what they are looking to hide.
It isn't just important for us to know if the majority of viewers think a fortnite walkthrough is shitty. We also need to know when a politician is lying to us.
Do most people think this is bullshit? That is what the like/dislike ratio communicates so succinctly.
If you want discourse about a video and its propagandiness then IMHO reddit would be a better place to get that because it has conversational features, unlike other social media spaces.
[1]: https://news.gallup.com/poll/354506/update-american-public-o...