Those can be decentralized, for PoS you can, for example, use pseudo-random selection process for validators, but there's many more things you can do. I'm not sure what knowledge you have about the blockchain "as a whole" but it doesn't seem to be that much. I'm not saying you're clueless but there's a bit lack of knowledge outside for what you actually know about "bitcoin" and the blockchain.

Blockchain has many proposes, you can use a centralized blockchain to do a lot with all the benefits that it provides (outside of it being decentralized) and there's many more practical and theoretical applications for it, you should study this and I'm not even talking about other coins or even crypto, this would only be valid if you really care about blockchain tech. and not only about one of the blockchains.

I'd suggest less self-centered thoughts towards Bitcoin.