btc would be worth nothing if it wasn't decentralised. I have no idea why a distributed network should have any value at all.
If it's not decentral it doesn't have any more value than a facebook-token.
Bitcoin is not decentralized, as
it is controlled by the Chinese mining cartel + Blockstream.
Yet Bitcoin has value.
Fiat money is not decentralized, yet it has value.
I would say it's still decentral but there is a trend to less decentralisation, that is true. Sadly that's an issue not many seem to care about.
It was even suggested to raise the blocksize when it was clear that would lead to even faster centralisation.
My quoted link explains that it is just an illusion of decentralization. It is by now already centralized, as evident by China+Blockstream making the decision to kill XT and Classic (i.e. a form of 51% attack control).