A framework is an important tool for any developer to master. Without them, we tend to reinvent the wheel with each new project.
A framework, though, is only a tool. The underlying language is a complete collection of tools, the framework being one of them. It is the box in which you keep your framework, any additional libraries you have created or use, and everything else.
If you only master a framework, you can only create those things that the framework is good at creating. Master the underlying language and you can create anything you can image.
Don’t be caught with a single tool in hand. Master the toolbox first and then fill it with the tools you use.