I actually don't have a problem with the Ranger itself, what I have a problem with is it's implementation in the game without it filling a clearly defined niche. Since I'm most familiar with the 3.5/Pathfinder version of the Ranger, let's look at that one; It has a full BAB, d10 hd, access to all weapons and armor (except exotic and heavy), limited access to Druid spells, and a very situational damage dealing ability in the form of favored enemy, and a very situational and slight boost to some skills with favored terrain. Now, what about any of that fills a niche that couldn't be filled by another class that took a feat? You say he is a wilderness warrior and survivalist? Sounds like a Barbarian. You say it has skills which are broadly useful in any environment? Sounds like Bards and Rogues. You even said that a Rouge could take over the Ranger's sneaking in a forest or dungeon. Again, it's the implementation that I have a problem with, not the idea of a Ranger itself. In a class based game, each class needs a role to fill, so if you want a "Ranger", then that needs to be very clearly defined, and be distinct from the other classes. As it stands, I don't see a mechanical or thematic distinction in the class.
That should also answer your last question about why we shouldn't keep it. If it does not fill a specific and distinct purpose in the game, then it should be removed. And I can't give an answer as to why it should be kept, because I can't see a reason for it. I'd even go a step further and remove the Barbarian, Druid, Sorcerer, and Monk. I think 5E also has a Warlock class, which is yet another flavor of Wizard. Now, to tie in your question about what would be gained from having less classes to choose from, with less classes comes less complexity, which in turn means it's easier to learn, which in turn is more attractive to those who have never played the game before. This is one of my complaints with Pathfinder. That game has so many rules that the Core Rulebook is 569 pages long, not including the Index. That's pretty daunting for new players. And if your game needs a "beginner's box" just to ease people into the game, it's too complex. The core rulebook should be all that is needed to get people into the game without getting a Master's degree in Law (I say, sarcastically to prove a point, because someone will take that literally). How about, instead of adding a lot of new classes and feats and spells and skills and races and archetypes and etc, etc, which create rules bloat and complexity, why not create a 5E version of Essentials, that boil the game down to it's essence? You might say that people like more options, but I would argue that less options allows for greater creativity. I know that the majority of sales is in the player options, but that's because they game companies don't market to GM's. Without GM's, there is no game. In order to keep up revenue, release more things for the GM to play with in the form of adventures, creatures, locations, what-have-you.
Kinda of a tangent to the original topic, but related, none-the-less.
*Edit: Sorry, this was a reply to Lord Twig, I forgot to hit "reply with quote".