> companies may discriminate against those candidates because they lack that industry specific skills (that otherwise could easily be picked up).

What does "otherwise" mean, here? The context we were discussing is that they asked you to quickly pick it up in a take-home assignment, and you couldn't pick it up that quickly. I don't see how this is them being shortsighted; it sounds like you just not delivering on the promise of your "fundamentals".

> the tooling or frameworks change but the core theory does not.

I 100% agree: someone who learnt MVC with Smalltalk in 1979 won't have any trouble picking up Rails' or Django's or whatever's version today. The concepts are timeless.

edit: to boil it down:

> these people should be able to pick up whatever tooling or frameworks on the job.

Yes, and if they can, they won't have trouble picking it up in the process of writing a take-home assignment. If they can't do that, then they just failed a litmus test.