As others have pointed out, the ranger can be a few different things. I think the class started out as a mix of a few related things, but grew out of control. It actually a good poster child for why I've become even more disenchanted by a class-based system -- I think it's stupid to use classes as bundles of abilities without archetypes, but I've found myself doing so more and more. Since the question makes no sense unless you're talking archetype, I'll go with that train of thought.
I strongly agree with everything in your post, but I want to point out that the Ranger
does have an archetype and that's why it
can be a class. Nothing wrong with a class-less system, but the Ranger works fine in D&D.
I don't blame the game if lots of people just look at the mechanics instead of looking at the bigger picture, think that the Ranger is just a bunch of lesser abilities, then proceed to envision an even more watered-down concept based on a couple of skills or weapon choices, and finally conclude there is no need for a Ranger in the game... it's a problem they created themselves. And pretty much the same thing can be done (and is done, in fact) on every class, see the periodic rambling about wizards and sorcerer begin too similar, druids should be just a kind of clerics, bards should be just multiclass combinations, barbarians should be just a background, paladins not much different than fighter/cleric... but all these are just part of the hobby of bored gamers to try and re-think parts of the games when they aren't playing it.
So it's not really that a class-based system is stupid, or that a class-less system is stupid. What is stupid is wasting time trying to turn a class-based system into class-less or a class-less system into class-based.
So, I’ve noticed that a lot of people who point to Aragorn as their quintessential embodiment of the ranger archetype also say that spell casting is an essential feature of the ranger class. This has always confused me, given that Aragorn never... uh... casts spells. Anyone who feels this way care to shed some light on this for me?
As I wrote in my post, for me the Ranger = Aragorn + spells.
Even tho I said Aragorn/Strider, I should have said Dunedain in general, not just a single character.
The spells addition to the Aragorn baseline is important because it tunes the archetype to the more magical world of D&D, compared to the less-magical world of Tolkien, and because it emphasizes the mystical-otherwordly nature of Rangers, thus strenghtening the archetype.
But it really matters which spells. If it was a subset of druidic spells it would not be good at all, and in fact when it happens, it dilutes the Ranger archetype into "part-time druid" and even forces some religious aspect which is not needed and just gets in the way. If it's a mix of different classes spells it's only slightly better, but still it suggests the Ranger is just scraping up random stuff from others, instead of having something of her own.
Have a more unique spells list as in 5e, and the Ranger herself gains a stronger identity. It's not anymore like the Ranger learning other's abilities here and there, it's everybody else who will not be able to do the same stuff unless they pick up a whole Ranger's life.
Then of course, allow multiclassing in the game, and you can just throw everything out of the window, but that's for another topic.