That might be a better word to use, maybe. But I'm not sure there was an adequate word for the point I was trying to make.
The linguistic definition of ideographic is that it is a language which uses symbols to represent concepts, rather than just literal pictures (pictographic) or sounds (alphabet or syllabrie).
Linguistics textbooks as far as I'm aware do not define symbol in this context, but generally a symbol seeks to represent the concept. Emoji are great symbols - you see an emoji and you largely understand its meaning, even if you have never seen it before.
The modern Chinese writing system is so abstracted that even an otherwise highly educated person that just lacks exposure to Chinese written script would have absolutely no idea what any of the characters mean. 一, 二, 三, sure. Beyond that, no fucking clue.
So yeah, they wouldn't be legible. Because as symbols, they objectively suck until you learn the basic components, structure, and patterns of organization of the characters.
So to the extent that an ideographic language conveys words as ideas through symbology, and to the uninitiated these symbols lack all meaning, it's not really ideographic is it?
But yeah, not legible might have gotten the point across better.