I was even as a junior the kind, who tried to understand the nature of the steps. I failed many times, but I learned from them all the time. I remember my mutable public static variables, and terrible small JavaScript apps. But every time when I did something like that, I tried to understand it. I knew that I failed. Sometimes it took me a year or more (like when I first encountered React about a decade ago, I immediately knew why some of my apps failed with architecture previously).

However, I've seen developers who were in this field for decades, and they still followed just recipes without understanding them.

So, I'm not entirely sure, that the distinction is this clear. But of course, it depends how we define "senior". Senior can be developers who try to understand the underlying reasons and code for a while. But companies seem to disagree.

Btw regarding functional programming. When I first coded in Haskell, I remember that I coded in it like in a standard imperative languages. Funnily, nowadays it's the opposite: when I code in imperative languages, it looks like functional programming. I don't know when my mental model switched. But one for sure, when I refactor something, my first todo is to make the data flow as "functional" as possible, then the real refactoring. It helps a lot to prevent bugs.

What really broke my mind was Prolog. It took me a lot to be able to do anything more than simple Hello World level things, at least compared to Haskell for example.