See the chapter: "Proper Use of Terms" (正名 zhēngmíng): A name becomes proper for a situation through conventional usage, but once this is fixed it is improper to deviate from this norm. "
Totally an ancient tech blogger
That said, I had a teacher years ago from Taiwan who argued that 1) Xunzi was the first full-blown "philosopher" (in the Western sense of offering an epistemology etc and arguing in a logically reasoned way) in Chinese history, and that 2) Xunzi and Zhuangzi were the smartest Chinese thinkers of all time. Years later, I'm not sure she was wrong.
That said, perhaps the Doctrine of the Mean wasn't considered all that important despite being part of the Book of Rites (礼记), or rather it wasn't considered prominent until around the Song dynasty.
荃者所以在魚，得魚而忘荃 蹄者所以在兔，得兔而忘蹄 言者所以在意，得意而忘言 吾安得忘言之人而與之言哉？
The fish trap exists because of the fish; once you've gotten the fish, you can forget the trap.
The rabbit snare exists because of the rabbit; once you've gotten the rabbit, you can forget the snare.
Words exist because of meaning; once you've gotten the meaning, you can forget the words. Where can I find a man who has forgotten words so I can have a word with him?
Although perhaps they are talking about two different things. Moreover, during Spring and Autumn into the Warring states period Confucius was e.g. changing the conventional usage of terms, e.g. what it meant or standards to be a 君子 (noble/gentleman).