There can be a completely de-centralized payment system in the future, when someone figures out on how to build an independent value stabilization mechanism. That crypto would become an actual currency, not a gimmick like bitcoin, that is dependent on fiat for valuation. Crypto can only beat central banks, if they do the same thing better then central banks. Meaning that they offer a currency with a predictable value and low service costs.

What can't be de-centralized, are people. There will always be people who are smarter then others and other people always centralize around them. This is not just human nature, but this is nature, that there are always strong that prevail and the weak that don't.  You can't force the world to be fair, because it just isn't. Some people are more capable then others and it is natural to reward them for that. Societies that have tried to to reward the weak and  suppress the strong (think communism) have only made a big mess.