It's not just algorithmic curation, it's the simplistic models of communication themselves - the medium. Reading this comment, you have no idea who I am, what my life experience is, what my competencies are, whether I'm a reasonable person coming from a reasonable place or just someone blowing off steam by repeating partisan propaganda. You might be able to discern some of that if you read my comment history or recognize my nick, but for the sheer majority of comments you're not going to do that.
So what you're left with is whether you find yourself agreeing with what I'm saying (In which case I'm a reasonable person you can trust!) or whether you disagree with it (in which case I'm one of those nonsensical "other" people that are part of the problem!). Voila, bubbles and polarization without even needing a malevolent intermediary.
Real name social media does fill in some of those details, but then its curation/editoralization also abuses those those details when it intermediates itself in the middle of your personal relationships and drives engagement using artificial social proof and whatnot.
That environment might even stand a chance if people had to type their full thoughts out as paragraphs, but instead people share links to well-written articles that satiate their desire for substantive analysis (although ultimately being chock full of groupthink that make their points inaccessible to the other tribe). And having had their desire for intellectual analysis fulfilled, people are then free to pump their own personal reactions full of vitriol.