I've spent a lot of time on learning these ideas. They are interesting in themselves, but also because they come with a tantalizing promise of usefulness. For m

I've spent a lot of time on learning these ideas. They are interesting in themselves, but also because they come with a tantalizing promise of usefulness. For me, that promise was never fulfilled. I suspect that's not just bad luck. Creating programming languages is mostly a practical problem, not a research problem. For example, type theory will never tell you that garbage collection is a good idea, or which kind you should use. My advice to younger folks looking at this field would be to turn back and instead solve some practical problem by creative programming. Git or BitTorrent would be good examples to emulate. Even a smaller project could have more impact than the whole field of PL research combined.