I don't really disagree with any of that and I'm not sure how that's a rebuttal. I think they can be complementary. "Filter bubbles" work as the discovery part

I don't really disagree with any of that and I'm not sure how that's a rebuttal. I think they can be complementary. "Filter bubbles" work as the discovery part that guides you toward the best communities (from your POV) and also gives directional information about their boundaries. If people are interested in learning about immigration and criminal justice reform and taxes, those topics will be amply covered in the community formed around their "filter bubble." If your point is that everyone should be interested in those topics, I think you're making a different point that is much harder to argue.