I don’t think that mortal programmers should be allowed to use 1st-class. They are no better than C’s “(*f)(x, y z)” stuff. (case in point: the JS-callbacks-using-anonymous-functions disaster)
CPS is just another kludgy attempt at making 1st-class functions more palatable to human programmers.
1st class functions *are* incredibly useful in toolbox languages, (aka High Level Assembler). 1st-class functions make it easier to create syntaxes (SCNs) with specific control flows.
People are “in love” with 1st class functions, CPS, promises, etc. They don’t notice, though that this is the same “power” as assembler put in programmers' hands in the '70’s.
Case-in-point: most programmers think that “multitasking is hard” and throw up their hands and just accept scraps from the dinner table. In fact, multitasking is easy, but you need to use an appropriate notation (SCN). Kids learn multitasking at the age of 5 (e.g. music notation). Only programmers think that multitasking is hard. Square peg, round hole.