Exactly. The problem is that even if the core service can be replicated in a decentralized manner on the blockchain, any periphery services (discussion boards, dispute resolution) need to exist in some centralized place, developed and maintained by some centralized entity. Hell, even the crypto code itself needs to be developed/maintained by someone. It's hard to avoid centralization when somebody has to do the work of maintaining the platform, because maintenance costs money, which requires stakeholders, who will not pass up an opportunity to "collect rent" if the platform has any sort of network lock-in.