I think that's a problem with civilization in general. It's how people work. I think we'd have to change human nature entirely in order to completely get rid of the echo problem.
No, that's far too simplified, I think. By that logic, either everything would have been an echo chamber ages ago or it is a process so slow that thousands of years of human development didn't progress it fast enough. If it's inherent to civilization and growing ever-faster over long periods of time, either the effect has happened, isn't strong enough, or it isn't inherent to civilization. I think it's the latter. An echo chamber effect happens when the community has a way of propagating opinions in a distinct direction and there is no significant counterforce. E.g: the opinion Potatoes are delicious is propagated in /r/potato because of people upvoting them, and there is no good counteraction because the people disagreeing with that statement probably aren't in /r/potato. So to answer the question of how to prevent an echo chamber is -I think- simply to do the opposite of what I just described: make sure opinions don't all have a similar direction, (e.g. all good or all bad) and make sure proper discussion is possible through counterarguments.
I think adding new influence halts the echo chamber effect. Everything hasn't developed into an echo chamber because humanity has been constantly expanding. We find new ideas, those ideas settle, and then we find new ones again. The echo chamber effect happens when you stop adding new ideas.
From what I've seen, the only way to deal with it is to add outside influence. You have to keep adding new voices, new ideas. The "Echo Chamber" question is basically asking how to prevent growth from halting. When you have a limited number of people discussing a topic long enough they will eventually reach a point where they can agree with each other.