"How long and often" people engage with content is a perfectly reasonable metric to optimize and a very close correlate of interest. There are, in fact, plenty of things going on in the world people should get mad about, or that they should worry about. Some people think that's climate change, some people think that's migration, some people think that's rising fascism, some people think that's Mamdami opening grocery stores. The fundamental problem people have is when other people get mad about stuff they like. That's the "fear", "anger", "hate." People who get mad about the things I like are obviously just irrational, emotionally driven puppets of The Algorithm whereas I am Englightened, Rational, and came to my opinions only through Reason and Logic.

What people don't like is huge masses of people coming together and having opinions that counter our modern mainstream elite consensus. Because elites are generally pretty smart that means a lot of these opinions are, frankly, dumb. Some of them simply represent different values (pro vs anti immigration, as one example.) Both are considered intolerable.

It is also perfectly true that people spend lots of time on non-politicized content. Baby videos, cat videos, feel-good human interest stories, all sorts of positive stuff is also massively popular on these platforms. That gets ignored in favor of inveighing for tight control over the political discourse because social media spreads crimethink.

The Western democratic ideal is that you have to convince the masses you're right - a disturbingly large portion of the movers and shakers have decided that instead, we should control what the masses are allowed to say and know, so we don't have to fight those battles.