Internet is centralized when a government can cut your access or limit it. It is centralized when you're paying your ISP for the ability to connect to the web.
It is centralized because somebody owns the cables. Those fiberoptics did not produce and lay themselves. Your local network at work is also centralized because someone owns the computers and someone pays the bills.
If your government cuts off your access, or your ISP turns off your connection....that does not mean the same conditions apply for every person in the world, that is a YOU problem, not an every person in the world problem.
There are millions of internet connections, many many ISPs and governments, the internet is decentralized, no one person or government can turn it all off, that will never happen.
Bitcoin is designed to be run on the internet, but can work any way that you can transmit data.
YOU can setup a satellite node and use bitcoin without internet. This is something setup precisely for people who have 'internet problems' in their country.
Bitcoin can work using virtually any method there is to transmit data, even radio waves, or infra red, but of course the web is the the best method.