Software engineering is an important skill to recruit for. Too many times I see "Java Developer"... Like, do they only know Java and are absolutely incompetent when it comes to something else?

I don't even want to recruit or be recruited with such a title.

Yes, but even then there are people who will ramp up faster.

If the company is using Common Lisp, do you have the 6-12 months to wait for them to ramp up, or do you hire someone who has done Lisp before? That is downstream from the technical decision to use Common Lisp, but it is a huge business impact.