The big problem with the exploration pillar in the wilderness is that it can be soooo easily bypassed. The various traveling spells make it so that a group, once a certain level is attained, can simply teleport right on the door step of the adventure area. A simple divination/scrying and voilà ! You have seen where you want to be so just teleport and the exploration pillar eats its shorts. By making the exploration pillar such a big deal in the ranger, they have cut a lot that could have helped the ranger in the other pillars.
What should have been proficiency in three skills became a much more codified thing that helps in the first two tiers but becomes almost irrelevant (if not downright useless) in the last two tiers. I know that even with all my years of experience, it is hard to actually keep the exploration feature of the ranger relevant up to 20th level. I can often manage it but at some points, some shenanigans become hard to justify and they also gimp the power of the casters that have the traveling spells that are normally used. Be they clerics or arcane caster, having a part of your spell selection off once in a while is acceptable. But if it happens too often, it becomes an irritation that can quickly become badwrongfun.
It's less that it becomes irrelevant as much as the game doesn't provide many examples of wilderness exploration.
Page 302 of the DMG is the start of lists of monsters sorted by environment and CR. In the forest, you fight a orc at level 1, and orge at level 2, a werewolf at level 3, a troll at level 5, an oni at level /, a young dragon at level 10.
The exploration challenges in the DMG are few. Gathering food in the forest is not a challenge for anyone over level 2. You 1d6 dys of food and water if you succeed foraging. You have to fail 4 checks in a row with 10 Wisdom to starve in a forest.
It's super easy. And you can buy food and bring it with you.
Basic forgaing, tracking, and navigation are super easy. A DM has to add complications to make them even challenges. That is without dealing with other exploration challenges like poisons, diseases, natural disasters, violent weather, fey trickery, shadow/necrotic sinks, dome/devil corruption, elemental enhancements, monster liars, primal fouling, etc.
The easy way to do wilderness exploration is to load the wilds with fey that mess with you. Then you can just do anything when the party strays of the roads too far. That's what my DM does. Thordamn tricksy fairiy princesses and their Alice in Wonderland nonsense.