On 31 March 2021, Cardano reached "100% decentralization" meaning that 100% of the blocks are produced by the stake pools.
An excellent introduction about Cardano decentralization is given here, but Cardano does have a Board of Directors (often known as "off-chain governance", as opposed to the "on-chain governance").
I wonder, to what extent (if any) could the "centralization" of the off-chain governance in the form of a Board of Directors pose a threat to Cardano's overall notion of being 100% decentralized from an on-chain perspective?