Blockchains do not have a monopoly on decentralization. People who assert this are trying to redefine the term to mean some kind of extreme P2P model that fits their narrative.
Almost all our traffic goes through Google, Amazon and Facebook. It's extremely centralised.
Blockchain a don't claim to have a monpoloy - they're just the most recent thing that's repopularised decentralisation.
If Amazon servers go down, so does a significant portion of the internet. That's centralisation at work!
Blockchain tech doesn't claim to have a monopoly on the term 'decentralisation', it's just re-popularised the technology.
So is bitcoin. Only 3 or 4 companies own the majority of mining.
Companies on the internet are centralized, but not the internet itself.
Still some issues with centralisation (since consesus is achieved through vote delegates), but that's much easier to fix than redistributing hashpower.