Copying other people's work has long been an accepted pedagogical technique. Painting students spend days in the museum, sketching away. Mathematicians in training work through the (difficult) classical proofs of important or interesting theorems. Writers write "in the style of" pieces.
The digital era, by making copying so easy, would seem at first glance to be a wonderous new era. Except that it's not.
The point of copying is to, by laboriously duplicating the steps used by the master, to train oneself in the same methods. It works well for painting, by repeating the brushwork of the masters, we learn something of brushwork. It works well for analog photography, by repeating the motions of burning and dodging, we learn something of burning and dodging. It works for mathematicians, by recapitulating the thought processes of the genius, we learn something of genius.
All of these things boil down to building a foundation of specifics from which we may and do generalize. We practice writing Dickensian description, and learn something more general about descriptive writing, something we can apply without being overtly Dickensian. We generalize to a collection of ways one might insert an adjectival phrase. We tweak and twist Dickens. We do the opposite.
In the darkroom, we experience serendipity. Practicing Adams' methods, we forget to set the timer, and in the ensuing disaster, we might learn something interesting. Indeed, my experience is that we're practically certain to.
Human laziness conspires against us. We would like to skip to the good part, to encapsulate the copying process neatly away, get through it in a few minutes, and somehow still gain the knowledge, which is impossible. It is only through the struggle, the boring tedium of copying, that we actually learn. Digital technologies are wonderful at eliminating this part!
Fast forward to now, get specific about photography.
Photography writing is 99% copied. People writing how-to guides simply crib the content from elsewhere, and often don't even understand the technique they're talking about. Missy Mwac and her ilk simply copy gripes from internet forums and expand them with boilerplate "humor". Even what passes for "serious" writing is, mostly, just lifted from elsewhere and slightly tweaked. The present blog, of course, is nothing but brilliance and original thought, though. Cut&Paste, Google, the haste to write something, and the desire for clicks have pretty much sucked the thought out of writing.
The pictures are also 99% copied. One of the most common themes in internet forums is "how does so and so get this look" (hint, it's always raising the black point until the picture looks all misty, or at any rate that's the answer you're going to get even if it's wrong). This is not in and of itself a bad thing, this is, sort of, how we learn. The trouble is that as soon as you see how to do the thing with the tone curve, then you save it as a preset, or make an action, and the knowledge vanishes.
The allegedly experienced photographers (Joined in March 1887, 120812981983 posts) all too often make it clear that they cannot look at a picture and simply see, in general terms, what's been done to saturation, hue, and the tone curve. Often, they can't see where the lights were placed with any reliability. They can't really guess very well at focal lengths, and most of them still get pretty muddled when you start talking about focal lengths relative to format. This should be basic stuff. I can do it, and I'm just some jerk on the internet. These guys may have been shooting forever, but they don't know anything about photography. A lot of that, I believe, has to do with the fact that they've mostly been copying ideas and methods in this modern digital era.
And that is the basic problem with copying in the digital world. It's so easy to make that tedious drudgery vanish, so people do. But the tedious drudgery is the point. Without the tedious drudgery, you're not learning anything.
It is as if a violinist who wanted to learn a technique of Itzhak Perlman were to simply buy a CD of the man's music and simply listen to it over and over. You're never going to learn anything unless you pick up your own violin and start sawing away on it.
So the takeaway. If you want to produce a specific effect by performing a specific well-understood manipulation in a Curves Tool, go do that manipulation by hand, every time. Don't convert it to an action. Don't use a preset. Go do it, by hand, every time. That way you'll never forget what it's actually doing, and you open the door to serendipity.
Generalize and apply, judiciously, the previous paragraph as necessary.