Which internet? The one we made or grew up with, or the one with ~4 gatekeepers that can very effectively keep you from participating in the vast majority of it for posting views they disagree with?
It has been easier. However if present trends continue and new forms of 'badthink' emerge it may be necessary to start looking under stones in dark places. This (a) is hard to do, and (b) presupposes that you know others are out there. Which you may not, especially if you are young.
So it's not that they are more isolated, just that hypothetically in a possible future they could be.
Yes. And then to stick to echo chamber with those people. So, fragmentation and balkanisation.