Sure. But in order to do central refactoring and actually improve stuff you need to keep in context all the small pieces.

You can split a small program into piece A, B, C All of them look correct on their own. But they duplicate something in 3 different ways and person/agent who can "see" all of them can see the duplication and refactor.

Current model context is simply not enough for large projects.

Same problem for letting AI review code. A PR might look correct on its own and be small enough to fit into context. But somebody who has access to the whole code of the project again sees the duplication.

I am an OSS developer and when reviewing PRs I actually look at how the same problem was solved in other popular OSS projects. No AI can check this today because there is simply not enough context.

Basically if we had unlimited context what you said might be true. But context size is limited today.