In fact the Internet has torn down existing authorities and given people the ability to create new communities as well as new authorities.
For example, climate skepticism explicitly posits that traditional authorities (scientists, the news, etc.) are wrong and seeks validation in creating new authorities and sources of truth. You might claim that these people are lacking in critical thinking, but any act of skepticism, no matter how ill-founded, is in itself an attempt at critical thinking. Same thing with anti-vaxxers -- nowadays anyone with a crazy theory can find an online community that validates their beliefs.
The internet has also majorly eroded trust in our existing institutions based on elite opinion and one-way media, while not creating replacements for those institutions. At the end of the day, one important role of institutions is to 1) make a decision and 2) get everyone to go along with it, even if the decision itself isn't perfect.
The Internet has provided the tools for everyone easily criticize and pick apart any decision, without providing a viable alternative means to come to consensus.
TL;DR you think the problem is institutions and authority, while I think the real problem is that the Internet is helping break them without putting them back together again.
Actually, I explicitly stated that I think the problem is humanity itself. Institutions and authority are one of the few things that keeps behaving well. Whether you are in the urban sprawl of Detroit and the luxurious gated community of Bel Air, if electricity and water are out for more than 2 weeks and there's no authority around (police, security, etc), things are going to get very ugly.
30 years ago if you had some crackpot theory, good luck finding anyone around you who agreed and would validate your beliefs. You'd watch and read normal news like everyone else and that was your source of information.
Nowadays you can come up with some strange idea, look it up on Google, and then find a bunch of other people who will tell you that you're right, the media's full of liars, and the scientists are all in it too.
Of course, this happened historically too before the Internet, but the difference is that in the past movements usually only happened in cities and college campuses and the like, because people had to talk face to face. Nowadays, everyone with a smart phone and some free time can self-radicalize.
Eventually society will notice this trend and people will adjust to it, but until that happens you're going to see a more fractious society with more people who won't believe anything anyone else says (at least about particular topics).
Basically, it might be the taught habit of critical thinking which actually makes people give up on the values which have been beneficial to modern civilization.
The act of civilizing entails removing danger from peoples lives. Danger provides the visceral motivation to abandon intuition and think critically. Reason can not convince an unreasonable person to expend the effort necessary to use reason. It's a Catch-22. You either forego civilization, at which point people will pursue critical thinking in order to save their lives and avoid suffering, or you build civilization, and guarantee that there is no tangible benefit to thinking critically.
An infrastructure built for a civilization must be maintained, but once there is not enough support in the civilization to do that maintenance, it will fall. And humanity will return to what might be reasonably called its 'ground state' of killing each other over superstition. (Lest you think people might realize their error once danger re-asserts itself as a few pieces of the infrastructure fails, keep in mind the profound difficulty reason and science had being accepted by society even when it was actively saving lives. And for a preview, read anti-vaccine folks, they are the vanguard. When one of the children in their community dies of complications from the measles, is it because they have allowed their ignorance to kill their own child? Ah no, it's because the rest of that pesky infrastructure still stands. They just haven't gone far enough...)
Even with those tools, the flaw ultimately lies within us humans as a species. The results of the Stanford Prison experiment and the Millgrim experiments show that humans have a natural tendency to obey perceived authority figures, even if it means going against our own ideals.
It's sad, but that's why history repeats itself. We are the same species as we were 70,000 years ago. It is our institutions, modern luxuries, and collective knowledge which make us civilized. Take that away we will probably act more savagely than people in dystopic, post-apocalyptic fiction. The bestial nature of humanity slightly reveals itself int he wilds of LA traffic. People will call you the worst things and hope that all the bad things in life happen to you for simply driving slowly because you are in an unfamiliar area.