[xyzzy_plugh]

What? There are most certainly tools which provide jump-to-definition for vim/emacs.

With respect to vim, at the primitive end of the spectrum is ctags. At the opposite end there are things like the fabulous vim-go, which provides all the functionality that you'd expect in a traditional IDE. There are many similar plugins for other languages.

Regardless, I contest the idea that you have to use an IDE. I find traditional UNIX tools more than sufficient for programming in any language. I can find definitions with grep, use ctags and vim's chugger to manage definitions across many files in many directories. I'm also not limited to the scope of just one project. The tools I use and my expertise with them can then be applied to any language or problem. I use the same tools to write emails and commit messages.

Large legacy Java programs may be frustrating, but they're not all that bad, and certainly don't warrant requiring maintainers to learn and use an IDE.