A barbarian is a rage-based melee combat juggernaut. A ranger is a hunter and tracker. In 5E, they share a grand total of zero unique class features (two if you count Extra Attack and Ability Score Improvement, which you shouldn't). The most you can say is that there's considerable overlap in their skill lists.
Fewer classes does not imply less complexity. A player only needs to learn his or her own character's class. That's where the complexity problem comes in for Pathfinder: loads and loads of build options that you have to sort through
within a given class. But it's really easy, and exciting, to tell new players "You can be a barbarian, like Conan, or a ranger, like Aragorn..." Then they just pick a class that matches their character concept -- and don't even try to tell me that the ranger isn't a distinct character concept -- and they don't have to care about any of the other class options unless they want to. You recommend having the role of the ranger be taken over by the rogue (or the barbarian or the bard, despite also advocating the removal of those classes

). That would actually make the problem worse, because it would mean putting those ranger options within the rogue class, making those classes more complex in a way that players actually have to care about. "Here is a ranger class" is simpler than "Here is a rogue class, and a feat that can turn the class into something ranger-like".
Reading this, I feel like you are writing from a position of ignorance about both 4E Essentials and 5E. Just for starters, Essentials had not one ranger class, but
two. And 5E has only printed one book that's even arguably "player options": the
Sword Coast Adventurer's Guide. Everything else has been adventure paths and the like.