I should explain a little further what I mean: there are "pure" ideograms even in English, like the & and % characters. These unambiguously refer to the words "and" and "percent", but the way they're written gives no clue whatsoever to a reader on how they're pronounced. If you had gone your entire life reading and writing English but somehow never encountered them, the way they're written is entirely unhelpful. Emoji are an even more abstract example, that don't even correspond to any word at all, just usually indicating mood or something like that.

It's a common misconception that all Chinese characters are like that, but my understanding is that while there are many, many more ideograms in Chinese than English, something like 80% of the characters do in some way indicate pronunciation (even if it's just something like tone) or use the "rebus principle" or something like that. So again, it's a spectrum, but all writing systems are phonetic to some extent. Human's wouldn't be able to use it to communicate effectively otherwise.

I will say that I'm not a linguist, nor can I read or write a word of Mandarin Chinese, and will happily stand corrected. This is just what I've picked up from reading books about the history and development of writing.