I say this in absolute all seriousness... I’m pretty sure that given a few decades, Warrior Cats is going to be analyzed by literary critics as completely re-codifying the anthropomorphic fantasy genre.
Because before Warrior Cats, we had... what? The Wind in the Willows? That’s almost completely based on English social mores at the time, and the animals don’t behave any differently from exceptionally small humans. Beatrix Potter? Same deal. The Chronicles of Narnia? Same deal, but with a religious allegory instead of a social one. Redwall? Most of the animals live in the titular abbey, so they’re pretty acclimatized to human culture, and we don’t hear much from the animals beyond. Most fantasy writers opt to take the easy way out and make their animal cultures a direct one-to-one comparison with human cultures.
The biggest pre-Warriors example I can think of that gave the animal characters their own customs and culture is Watership Down by Richard Adams. Watership Down gave us naming conventions for the rabbits, words they use for human inventions, a mythology similar to Kipling’s Just-So Stories, and even a numbering system (rabbits can’t count above the number five, so anything above that is just generalized as “many”).
As far as cats go, before Warriors, the closest thing we had to “cat culture” was--I shit you not--Old Possum’s Book of Practical Cats, which gave us the idea that cats have a “family” name that humans call them, a “more particular” name that other cats call them, and an “ineffable” name only they themselves know, like a True Name in fairy mythology. Warriors doesn’t use this, but instead it sticks to vocabulary that cats in the wild would already be familiar with, and it uses honorifics for leaders and apprentices of each clan like “star” and “paw”. The “star” is interesting because, since the leaders are chosen by the revered ancestors of StarClan, it denotes the divine right of kings--cat leaders are literally ordained by God, or the closest thing they have to gods (there is no single higher power in Warriors). Moreover, it’s probably the only anthropomorphic fantasy that doesn’t resort to its own conlang in some way--it communicates everything in simple language that both children and (presumably) wild cats would understand. So the Erins can describe naming conventions, foreign territories, ancestor worship and religious practices, the concept of reincarnation, and the cat equivalent of hell in a relatively grounded way that’s relatively easy to translate and doesn’t require the readers to learn a new language through context clues. Literally the only example I can think of that comes close is The Guardians of Ga’Hoole, but even then there’s a few uses of “owl language” that readers might not pick up on immediately.
I’m willing to be corrected on this if there’s any details or nuance I missed, but I completely stand by my thesis.