Note this framing: centralization is not necessarily harmful, decentralization may not address problems and may cause new ones.
Rather than a rallying cry for decentralization, it's a call to preserve the increasing status quo: yes, it's worrying large corporations are centralizing the internet, but should *standards* really be worried about that?
More from the RFC:
> [...] approaches like requiring a "Centralization Considerations" section in documents, gatekeeping publication on a centralization review, or committing significant resources to searching for centralization in protocols are unlikely to improve the Internet.