It cannot be mined and the developer holds a lot of supply. I think that's the reason it's called centralized.
The BSC referred to in this case is the blockchain and not any token. It is considered by many people as centralized since there are only 21 validators compared to the thousands of nodes on the Ethereum chain. Less nodes means more control. More control means more centralized.
Giving that fact, those nodes holders can control most of the movements of this chain, I follow you with your statement. It's assumed
centralized as control are being dictated by few.
It is centralized, that's why I don't really see it could compete against ETH although ETH platforms now charge a huge transaction fee. People transfer to BSC due to its lower fee but when ETH could sort and run the ETH 2.0 successfully, people will start coming back.
For now, Yes it's been use as alternative since ETH gas fee really taking small investor's down. Traders who can't afford to
pay the transaction fees will find and willing to use alternative to continue doing business.