My own realization that I'll probably never do anything on the frontier of language design hasn't killed my interest in designing a language, but redirected it.

These days my thoughts drift towards novelty and niche domains. What would be the most interesting way of describing a subset of things? The most fun? The most intuitive? What's a way to break a specific domain down into a vocabulary that lets you populate it while forgetting you're even using a computer?

I think there's still a lot to explore even if you aren't shooting for maximum productivity or even general-purpose programming.