In React's case, it's meant to pretty much entirely focus on the process of (input data -> output DOM nodes), plus the minimal set of wrapper functionality need

In React's case, it's meant to pretty much entirely focus on the process of (input data -> output DOM nodes), plus the minimal set of wrapper functionality needed to handle user input and general asynchronous data loading (class-based component state, context loading, and most recently hooks). It intentionally doesn't handle a lot of stuff like dependencies (that's a job for your bundler), the actual data fetching, the actual specifics of your UI, centralized global data management, etc.