Echo chamber is a symptom of a deeper issue. If you want to have a quality opinion on something, then you need to do serious work on often-gated information.

Without that hard, often-gated work, how is anyone supposed to form an independent opinion on something like global warming, models of crime, economic policy, intimate relationships, pedagogy, and so on? So what you're seeing is not the discussion of ideas, but rather the negotiation of clan policy and identity.

There's no policy that you can implement to stop this "echo chamber" or "groupthink", which are merely symptoms of a deeper issue: that the antecedents of independent opinion on a wide range of phenomena are simply not there, and that obtaining quality is resource-intensive with non-trivial opportunity cost.