I've always thought of the Oath of the Ancients as a fey knight, a paladin beholden to archfey in a similar way to a fey pact warlock. It is the paladin oath of choice for any elven paladins that I might make.
Ooh, I like this. That's short and sweet, but also sufficiently not-abstract to be useful in play.Ancients seems more "natural order" rather than "civil order". Hence the association with nature rather than society.
The way I see it, it's like a druid-themed version of the paladin. Where a paladin is already just a slightly-more-martial version of the cleric, this weird variant paladin is a slightly-more-martial version of the druid.
There's no point in digging too deep or second-guessing beyond its obvious appearances. A character class is supposed to represent an iconic character archetype, and pretending otherwise is counter-productive.