In my view, there's not really a ton of other directly measurable things. We can ask users all kinds of questions to try and gauge what impact we're having, but that takes extreme work, doesn't scale, & has all manners of awful self-reporting bias.

By contrast, using whether or not someone keeps watching & how much they upvote/interact does not seems like some horrible end of times disaster. Which is basically what engagement is. It's a directly observable metric, and it correlates pretty closely with whether or not what you are doing sucks for users or is something they seem to enjoy enough to keep doing.

Are there bad aspects? Yeah likely. But to me, 99% this looks like trying to make a product people enjoy & like to use. Having such a strong opinion as you have, describing & attributing so many horrific negative effects - for making a product that has a measurably positive impact on basic user enjoyment - seems a bit wild to me. It's the tendency to view technology as magic, as some phenomenally super powerful ultra-capable advanced wizard-machine with incredibly fine grained & exact & perfect control. It's just not so. There's just not that much knowledge or sense inside the system to know what it's recommending or what it's doing, it's just blindly following macro-trends to try to make some course ass suggestion that maybe might help.

There probably are some fairly gross/bad decisions that are bad for users being made, and there is definitely some shaping of intent, choice of what to push - a man behind the curtains of the algorithm, picking some biases, and some of those choices are probably closer to hell than heaven, but overall I just don't think there's that much real control or competency in how we pick stuff, in how these choices are made. I wish I could find it, but there was a wonderful critique of Zuboff's Age of Surveillance Capitalism that said, yes, the situation isn't great, but the book is also overselling the powers & potency these systems have. They're just not that smart, not so well guided as to be the high-functioning brainwashing machines the modern mania has made them out to be..

And I think it's selling enormous fear to worry so deeply that "It's warping user's minds, addicting them, and polarizaing them". Overall I think that describes such a vanishingly small problem, such a non-phenomenon in the global scale of things. Very very very few people fall down these dark paths. Countless more have perfectly fine experiences, experiencing no or only the most mild side-effects of the bad side. It races into paranoia to exacerbate the problem & magnify only the bad so heavily, leaves rationality behind & portrays a clutching desperation. It's the "the cities have become unlivable hells" narrative, but virtual: the online world has become an unlivable hell. Please, I feel like we've lost moderation, are spiralling out into wildness. Not everything is amazing, but it's just not so bad. Such a willfull blindness & such extremeism to ignore so very much of the picture & radicalize yourself around Fear Uncertainty and Doubt. and that position leaves us so weak, so susceptible to influence; there are real problems & real despair a plenty in the world, but youtube is, like, not really a huge factor in that, at all. It barely has a mark.