But in a lot of cases you can't know all the dependencies, so you lean on the community trusting that a package solves the problem well enough that you can abstract it.

You can pin the dependency and review the changes for security reasons, but fully grasping the logic is non-trivial.

Smaller dependencies are fine to copy at first, but at some point the codebase becomes too big, so you abstract it and at that point it becomes a self-maintained dependency. Which is a fair decision, but it is all about tradeoffs and sometimes too costly.

You'd get those benefits from traditional dependencies if you copy them in and never update. Is an AI dependency going to have the equivalent of "upstream fixes"?