It's true that it would be technically trivial for Apple to censor web access on iPhones. However, they don't do this, and it doesn't seem reasonable to expect them to in the future.
Sandboxing apps / discouraging side-loading are categorically different than going the way of Communist China.
Where is the user value in censoring web sites?
You don't believe the Chinese government would force companies that want to do business in China to censor things they don't agree with or you have failed to notice the US trying to force companies to use compromised encryption so that they can spy on all communication?
Apple can always threaten to walk away from China if they request something like that. Apple also doesn't play nice with the FBI over those kinds of requests. This fantasy of yours is just getting wilder and wilder
Its trivial to censor if you don't have a right to install the software you prefer.