I agree in that a pure framework is just a design pattern and that would be easy to implement. The really useful part of these frameworks is likely the libraries they are bundled with. Sure, somebody with the right experience can duplicate all the work of another person but there's obviously the problem of the duplicate of effort and the waste of time. In the case of code that have many users it is also benefiting from the experience of a large community. If the framework/library is open source there's really nothing preventing you from become familiar with the parts of the code you use. When it comes down to it I don't think it's really a matter of developer experience so much as the time it takes to learn another person's code and managing the risks of that external code changing. Really it seems there are benefits to each approach but certainly there are many benefits to using community developed code.