Sounds like it was taken from Campbell's Hero's Journey.
It isn't an imposition. It's simply an analysis of the oldest story we tell. It appears in the vast majority of the stories we've ever told, and is still widely used today. Scrooge would be a Heroic figure, according to Campbell, and his story would follow the Journey closely. I'd have to sit down and analyse it to see how closely, but I'm sure it's pretty tight.
It's really not a "vaguely defined philosophical/pseudo-psychological construct." It's actually quite an accomplishment in literature in general, and mythology in particular. Campbell was a fine scholar. I dig him.
http://en.wikipedia.org/wiki/Monomyth
On the other hand, well, let me illustrate it with a parable
My parents were in the habit of renting a lot of movies, so I ended up seeing a lot. And at some point in high school, it dawned upon me that whole genres followed the exact same script with different names and props. If you knew how long the movie is, what genre -- say, action movie -- and saw about a quarter of an hour of it, you could tell not only that the hero's love interest will be kidnapped, but also by who and exactly when in the movie. It didn't matter if it was some SF movie, or swords-and-sorcery fantasy, or modern day story of vengeance, etc, you could just tell that that guy will kidnap that gal, and the other guy will go save her. Which pretty much killed my interest in movies right there.
Now I COULD have concluded that simply that's the one story that humans always tell. What I actually concluded was just that Hollywood does reuse the same script over and over again, just changing the names and props. Turned out it's right too: those guys don't just naturally happen to produce monomyth after monomyth, but have whole schools and consultant agencies to turn anything into an exact monomyth implementation. Because implementations of it sold, and they just want to make more movies that sell.
Now I'm not saying that just to say that I'm smart (usually having to tell people means the opposite is true), but it looks to me like the same really happens to those stories Campbell looked at, IMHO.
The thing is, all those stories with similar plots didn't really appear independently and in a vacuum. People actually read existing novels, before deciding they want to write their own, and the same happened in ancient times too. And people came up very early with the idea of reusing the structure of something that was very popular, because they wanted their story or play to be very popular too.
E.g., in the Greco-Roman world and around it, very soon they started using Homer in the same way Hollywood uses the monomyth nowadays. Writing something specifically after the structure of Homer was actually taken as a sign of being an educated man. And they did it lots. You can tell how popular it was when even the gospels in the bible use that structure.
Or speaking of the Bible, you can tell the difference in quality between the first four books, which are just full of long "X begat Y" lists and whole chapters of lists of rules, and the stories added after the scribes came back from Babylon. Then you start getting fantastic stories like Jonah or Tobit or whatnot, that follow better narrative structures. You can tell that they learned SOMETHING in Babylon.
And stories from other cultures, or folk stories, ultimately have the problem that we have very few that are the raw form of them. Many were collected and redacted in forms also closer to what was known to make a story that sells. E.g., I'd be willing to bet that if you found some Norse stories from much earlier times, they'd be a lot less fanciful than Snorri's versions.
But really, you'd be surprised for how many things they already had standard narratives, and standard structures. E.g., even the physical description we have of Charlemagne for example is taken to be probably not very descriptive of the actual man, but rather a standard description of a noble king. And while Charlemagne is a late case, they did things like that at least as early as Alexander, actually. And arguably even earlier, as Egyptian pharaohs had a standardized description and appearance for as early as we have any depictions of them.
They even had what we now call deliberately subverting a trope, to draw attention to something, quite early in BC times.
What I'm saying is that at the end of the day, yes, Campbell is right, there is basically a monomyth, but simultaneously that doesn't really mean much. A lot of stories are similar just because they all plagiarized the structure of the same stories. It's basically like noticing that High School Musical has an awful lot in common with Romeo And Juliet: it's simultaneously both true, and really not meaning much than that the screenplay was actually based on Romeo And Juliet.
