There's a class of "crystallized intelligence" jobs which are about what happened before rather than what you do today. There's an intersection between that sort of knowledge and a certain fluid intelligence to slot it in where things fit.
I'm in one of those jobs right now, where the last six years of what I've read/absorbed is more valuable (as a sort of fast cross-reference in my brain) than what I actually do right now. I'm the guy with the picture that's on puzzle box, rather than having to place each puzzle piece.
I've tried really hard to make myself obsolete and do something else, but it has backfired spectacularly.
I've written down all of this in documents, trained other people to do the same thing over the years, even built tools to replace the easy parts (right now there's an intern doing the next pass of that automation) the effect of which has been to lighten my workload even more & I'm not missed if need to take a couple of weeks on a roadtrip or something.
To do this, I've had to do something which is not volume driven (i.e my output is not a factor of time), so moved away from building web applications to profiling/optimizing all kinds of networked applications, where the ability to cut through the stack is useful, but for any given layer there's someone who does it "professionally".
This is of course not a long-term parking spot for me, but I'm useful and in essence acting as "an elder" store of information about the past & a slightly clearer view of the future.