I think it's insulting to say that human opinion or observation is worthless because a small program with a neat dataset can answer a lot of questions.
It's like saying that talking with friends about history and engineering is boring because wikipedia has the answers.
I mean, as an individual it is a choice. But as a society it’s not a choice (or, maybe, a better way to phrase it is the “mainstream” is a reflection of the choice society has already made)
I feel like we're getting into "the raindrop doesn't feel responsible for the flood" territory here, and I like your second interpretation better.
It's absolutely the choice society has made, but society is the individuals that make it up. The idea of the group is a semi-useful abstraction we use because our brains have trouble conceptualizing numbers over ~17.
The style of algorithmic feed was created and popularized by individuals about a decade or two ago. A lot of the users of this site (including me) were pioneers in that area, either creating these things, or being the first users to turn our lives over to the feed.
But, if you want to create long-lasting societal change (either good or bad), that's how you have to do it. One individual, or a group of individuals start something. A few individuals (usually weirdos) join up. And at a certain point, the increasing number of people give other more mainstream people some sort of social permission to make the same choice.
At some point, it becomes socially acceptable enough to become the default and people who don't have the time or energy to put a lot of thought/research into things start doing it without really thinking (this is generally where I consider the bounds of true mainstream).