You hit the nail on the head I think. A few years into my career I was enamored by learning new programming languages, in particular functional ones. I was fully drinking the koolaid, too - pure functions and immutability would surely make writing web crud a blissful experience, right?

At some point I realized that the nice examples from the books never mapped to the real world as cleanly. Exceptions were pretty useful, local mutability made lots of things easier, and category theory has no place in calling JSON apis over http.

I think a great number of talented programmers never learn that lesson, and continue futzing about with theoretical purity for its own sake.