The Bluesky app view is centralized in that it can decide which content to show, but A) the hosting of that content is decentralized, and B) alternate app views like Blacksky exist which are fully independent of Bluesky (both Bluesky the company and Bluesky the app view). The Bluesky app view could stop showing users content from Blacksky (or any other) PDSes, but that's it. If you're using the Blacksky app view, afaik Bluesky the company can't do anything other than cut you off from Bluesky's PDSes.