I think bitcoin is still decentralized because we can still do a peer-to-peer trading of different cryptocurrency.
i think p2p is what makes it decentralize because other centralized payment methods can do p2p trading too but the only difference is cryptos can hide your infos if you wanted too but cex payment methods are i think not possbile and i often see you and the other traders details after every transaction ,
Even though it is managed by a huge mining farms, as long as it's managed by the central authority or government, it will still be in decentralized. As long as the number of people who uses bitcoin, the more it will become decentralized.
its not decentralized if its manage by someone . btc isnt manage by mining farms but no one owns btc , though we need miners to process the transaction . increasing number of btc users dont also indicate for a more decentralized economy .