The problem is that the choice of language to learn next is not signal for any of those points. With so many languages and platforms, one has to prioritize base

The problem is that the choice of language to learn next is not signal for any of those points. With so many languages and platforms, one has to prioritize based on something. Job prospects is a perfectly fine criteria, even for someone who is curious and not lazy. It's a signal for pragmatism, and that's it.