I think it's kind of strange that OP's focus on the framework as the way to determine how replaceable people are. I think unless required, most people have basi

I think it's kind of strange that OP's focus on the framework as the way to determine how replaceable people are. I think unless required, most people have basic familiarity with a framework, and are likely more familiar with the languages that make up said framework. Any Javascript framework or stack (outside of something obscure) is easy to learn (read: doesn't take any real special skill) especially if there is an existing codebase that developers can use to learn from...