It's semi-decentralized because of fiat exchanges. At this time you're unable to do anything without a middleman in the form of an exchange. Note that payment processors are also exchanges, just more automated.
You buy Bitcoin with fiat to enter the crypto sphere and fiat is centralized and traceable. Then you put it on a centralized exchange where usually you have to get approved and share all your private data. Then you still cannot spend Bitcoin without a payment processor or an exchange unless you agree with someone that they will take Bitcoins directly from you.
That's not true, exchanges and payment processors aren't part of Bitcoin's protocol, and it's possible to use Bitcoin without them. You can do direct p2p trades to trade fiat and you can look for places that allow you to spend Bitcoin directly. I get what you are saying, but it's ambiguous to say that Bitcoin is semi-decentralized, and less knowledgeable people can see a wrong picture from it. Fundamentally Bitcoin is as decentralized as it has always been.