Bitcoin network remains decentralized, and it will stay like that with proof-of-work, but distribution of coins is changing after Blackrock entered the market and start buying coins.
This is not the only company who decided to invest in Bitcoin, but they have most power to manipulate markets because they are majority owners of most assets in the world.
Everyone can help decentralization by running their own nodes, using non-custodial wallets, and decentralized exchanges.