Decentralized means no one controls it even central bank cannot control it because its run by its users that composed bitcoin if it will become centralized then theres no purposed using it what we need is proper regulation of the government on how we can fully utilised it legally.
Exactly. There would be no purpose to use Bitcoin if it's centralized. A centralized system is prone to extreme manipulation from governments, and other entities. For example, EOS' Block Producer have been able to freeze accounts and restrict some users access to the "blockchain" because the platform itself is extremely centralized. Because of this, cryptocurrencies such as Ripple (XRP) and EOS are considered by many individuals as another banking system.
On the other hand, Bitcoin has been able to obtain success for quite some time because it has retained decentralization (although the mining process has become more centralized over time due to the creation of mining pools). If by any way, Bitcoin becomes centralized, then it'll be doomed as people would look for other alternatives which are decentralized. Compared with other cryptocurrencies in existence, Bitcoin may not be the most decentralized option nowadays. An altcoin known as Ravencoin is ASIC-Resistant with decentralization in mind. With this, the cryptocurrency could perform at a higher level of decentralization than Bitcoin, since no single entity or company is in-charge of the mining process. In Ravencoin, you only mine with GPUs which is a far more accessible option than Bitcoin's ASIC miners nowadays.
Another cryptocurrency known as Magi, is also more decentralized than Bitcoin, since it has adopted a unique PoW algorithm known as M7M which focuses on small miners rather than big miners with a lot of hashrate. This allows small miners to easily secure the Magi blockchain, as the higher the hashrate on the network, the lower the block reward will be. Being a hybrid PoW/PoS cryptocurrency, Magi balances between mining and staking to obtain a greater degree of decentralization than most cryptocurrencies we know and love today.
Nonetheless, Bitcoin is still decentralized but it could've been better if somehow mining pools would become disincentivized. That way, full decentralization could be ensured as small miners (or the average Joe) would be able to participate in the consensus and security of the Bitcoin blockchain. However, that's up to the developers and the community to decide whenever it's best for Bitcoin or not. Just my thoughts