Most of the internet is made up of echo chambers now even though anyone and everyone can access a majority of it. I don't think being selective in who we allow into communities worsens the pre-existing echo chamber issue. If anything it may help to be more selective. It can sometimes be impossible to tell the difference between trolls, bots, and real people, so I feel like we assume every person we disagree with is a troll or bot. The issue with that is that we may be outright dismissing real opinions. In theory, everyone in a selective community is a real person who is expressing their true thoughts and feelings.