I think this touches on a great point. People envision the ranger, or any martial class, as doing something heroic at higher levels. Trekking across a dangerous desert or exploring some ancient ruins in a forest are par for the course for our ranger - at least that is what we envision.
But when you look at the challenges at those higher levels, there are only a few that match our expectations. Many of those desert monsters (Yuan-ti, young blue dragon, efreeti, mummy, etc.) are too diverse for the ranger. That said, I think the same can be said for
all the other classes too. While we envision Aragorn searching the ruins, the truth is, if a character at higher level is alone, and comes across a foe with a CR close to it, there is a good chance they lose. The only exception I can think of is if the creature specifically matches the strength of the class, ie. a barbarian fighting a yuan-ti abomination or something melee centered.
In the end, I like this design, as it helps keep the focus on the group. It helps the fighter understand their three melee attacks do nothing against four manticores raining down spikes, and the warlock happy that the fighter is there to take damage from the purple worm.