I'm pretty sure the issue is not "higher order abstractions". It is using multiple single letter references with no real grounding or relationship that the reader has to track.

For example, looping over a map with "k" and "v" vars is not that bad because the reader understands k=key and v=value, and that makes since for a map. If you do this same thing with different single letter vars, e.g. "a" and "b", it instantly becomes more difficult to read.

When writing a generic function and using these single character type references it can make sense, especially because the function/method doesn't care what those references are, however to someone trying to understand what's going on it can be extremely difficult simply because of the names.

Sure, if all you are going to do is call that method or function those type references go away and the call site may be relatively clean, but you still have to read the thing to understand what it is and how to use it.

On the contrary, linq in C# is a killer function that other languages still fail to replicate.

How many sloc are required for this?

var max = mycollection.Max();

Probably 5-10 if you’re missing higher order functions. And the risk of bugs will be 10x.