Being able to handle Bitcoin transactions is fine, but it's disingenuous to act like it's the only way to be truly decentralized.

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.