Hinges on you definition on truly decentralized. ETH is not truly decentralized (and never will be since their shift to proof-of-stake) as there is no way of not-knowing that the majority stake is not in a single force (or a conspiring group) - which in theory could already be the case. Absence of the counterproof and presence of a case where it would be centralized can never make it truly decentralized.
That's not really a valid criticism. You can say that same thing about any protocol. Who's to say that the majority of btc hashing power isn't single force or conspiring group?
