Do not comment. Not at all. Not even if you can avoid being toxic. It is unlikely to be appreciated and likely to accomplish anything.
Just quietly dislike the video, so the bot does not reccommend it to you again.
And if it is a subject that is really important and that you actually know about, then share your thoughts in your own place. But not as a response, just say your thing.
I always saw youtube comments as a sort of /dev/null to begin with. The only useful comments I've ever seen are the people that post time stamps for different locations in the video.
Invidious.xyz is a nice, light weight, alternative front end to youtube. Might be of interest in this case.
Edit: i see what you mean now. Yes, I agree. It's not a good medium for that kind of thing in general.
Why sign into YouTube at all? If you see a video you like, run the URL through mpv; it'll use youtube-dl in the background to download the video so you can play it without buffering or dealing with webshit.
My caveat to this policy is:
Are they fairly new to the game? Would constructive criticism be beneficial? If you're the audience for the video perhaps viewer insights could be helpful. Or obviously, if they solicit feedback on maybe a new format/show/concept.
Especially on youtube, leaving a comment can go along way in the almighty algorithms eyes - so if you didn't like a video but like the new creator - let them know your thoughts (nicely). If they don't care, they don't have to read it.
That being said: I always laugh when I see a video with millions of viewers and people commenting like 'this content sucks' like bruh it clearly isn't for you, thumbs down and move on - or click the menu and tell your feed to not recommend this type of video/channel.