It looks like even with an unfiltered world, echo chambers still evolve. It's the nature of communities.
>Do we really need more 4chans?
Yes, if by "4chans" you mean anonymous platforms. That doesn't necessarily mean we need more of the toxicity at the bottom of the cesspool that imageboard culture is known for, but I do think we need more sites which push back against the hostile patterns of social media, which include "real name" policies and moderation or filtering that tries to shape communities from the top down.
The truth here is that one person's echo chamber is another person's culture, and that "unfiltered" is just another kind of echo chamber.
4chan is clearly less filtered than reddit, and we can see how differences in the degree of filtering creates a race to the bottom.
4chan is too restrictive for some people who want to race to an even deeper bottom, and on and on.
>That doesn't necessarily mean we need more of the toxicity at the bottom of the cesspool that imageboard culture is known for
But the whole point is that the less filtered the community, the more a toxic lowest common denominator develops, which is not preferable to the things decried as "echo chambers" in more filtered communities.
I mean there has to be some reason people spend their time there.