Centralization has nothing to do with the problems of society and technology. And if you think the internet is all controlled by just a couple companies, you don't actually understand how it works. The internet is wildly decentralized. Even Cloudflare is. It offers tons of services, all of which are completely optional and can be used individually. You can also stop using them at any time, and use any of their competitors (of which there are many).

If, on the off chance, people just get "addicted" to Cloudflare, and Cloudflare's now-obviously-terrible engineering causes society to become less reliable, then people will respond to that. Either competitors will pop up, or people will depend on them less, or governments will (finally!) impose some regulations around the operation of technical infrastructure.

We have actually too much freedom on the Internet. Companies are free to build internet systems any way they want - including in very unreliable ways - because we impose no regulations or standards requirements on them. Those people are then free to sell products to real people based on this shoddy design, with no penalty for the products falling apart. So far we haven't had any gigantic disasters (Great Chicago Fire, Triangle Shirtwaist Factory Fire, MGM Grand Hotel Fire), but we have had major disruptions.

We already dealt with this problem in the rest of society. Buildings have building codes, fire codes, electrical codes. They prescribe and require testing procedures, provide standard building methods to ensure strength in extreme weather, resist a spreading fire long enough to allow people to escape, etc. All measures to ensure the safety and reliability of the things we interact with and depend on. You can build anything you want - say, a preschool? - but you aren't allowed to build it in a shoddy manner. We have that for physical infrastructure; now we need it for virtual infrastructure. A software building code.

Centralization means having a single point of failure for everything. If your government, mobile phone or car stops working, it doesn't mean all governments, all cars and all mobile phones stop working.

Centralization makes mass surveillance easier, makes selectively denying of service easier. Centralization also means that once someone hacks into the system, he gains access to all data, not just a part of it.