Voting on a commercial platform isn't an expression of free speech. The commercial platform doesn't owe it to you to keep your desired features around forever. The comment section still remains. Further, if you don't like a video, then don't press the like button. You aren't being made to like a video once you've watched it.downvote was an expression of free speech that any sane person liked as it showed peoples discontent on propaganda etc.
I even just read that the dislike count can still be perused by the video maker. So your "expression of free speech" is very much visible to them. You not seeing how many people agree with you seems like a you problem.
For the second part of this, the most downvoted lists mostly contain music videos, trailers people didn't like, and the most downvoted video was apparently the YouTube rewind from 2018. None of them would read as "propaganda" videos to sane people, as you say, just bad videos.
The simple fact is, most sane liberal leaning people tend to watch liberal leaning media. And most sane conservative leaning people tend to watch conservative media. And some sane people from both ends engage in meaningful discussion through comments, and certainly not through upvotes or downvotes, because they know they're not 5 year olds. Some mobs going out of their way to downvote bomb what they perceive as "propaganda" is them being mobs of insane people. Or 5 year olds.