So, if I was in charge of a new PHB, here is how I would define the Ranger:
“The Ranger is the Warrior of the Frontier, the one who exists between two worlds. Rangers protect settlers from the assaults of wild beasts, they protect Nature from the wanton destruction of Man, they stalk the borderland between enemy kingdoms, or they guard the World against those that would invade from another plane. These situations naturally develop in a need for novel tactics, employing might and cunning in equal measures, and they often lead to living in isolated conditions where knowledge of your surrounding and self-reliance are essential for survival. This combination of skills and traits makes Rangers incredibly well suited to the life of Adventurer, and are regarded as some of the best companions one can have on a long quest.
While all Rangers share certain traits, the relationship they have with the different Worlds they straddle marks them in unique ways, making them stand out from each other. They might look totally different to an outsider's perspective, but two different Rangers who meet for the first time will often realize their commonality and quickly bond over stories of their personal Frontier."
Every subclass would thus be defined in what frontier it straddles, rather than purely it's favored foe. Some would be purely martial, others would have picked up magical skills.