I would say "yes": the interesting part of building a framework comes from taking a deep understanding of a problem domain and generalizing it so that others can take advantage of what you learned. As this is not what you will be doing, you won't actually be getting the associated "experience". That said, you will not be "wasting your time" (you can, after all, sort of simulate this experience with superficial knowledge), but there are probably numerous more direct things you could be doing.
Thank you saurik, I'll save the framework for one of these occasions. Any suggetion what a "more direct [thing]" could be to become a better developer? I'm currently working on privly (https://github.com/hery/privly-ios), reading iOS dev books, open-source code, and blogs.