But it did. It took around 1500 years from the first writing systems to fully phonetic systems. And we still have Chinese characters even now, or the Tibetan writing system.
For some reason, writing systems tend to stay stuck on mixed logographic and phonetic systems.
The earliest evidence for this in cuneiform is from around 3200-3000 BCE. There is a famous tablet where the symbol for "reed" is used to represent the word "reimburse", because they're both pronounced like gi. By a few hundred years later, cuneiform was a fully fledged phonetic writing system.
Phonetic use of the characters was immediate. The go-to example here is 來, which depicts a stalk of wheat. It is the spelling of the verb "come", and the verb is spelled that way because the character for "wheat" was borrowed with no alterations to represent its own pronunciation, which was shared with the verb.
It's a mixed system with about 2 millennia of legacy. It started as logographic, then it got into phono-semantic compounds, with detours into the written-only official language (like Latin), and now it's messy mix of everything. There are true logographs (休，林，森), true phonosemantic compounds, and plenty purely phonetic characters that have no meaning by themselves ("bound morphemes").
Don't confuse the origin of the system with what the system is now.
Using your example, what do you see as the difference between the "logographs" 森 and 林?
Neither can be a logograph, because neither one represents a word. But even if that weren't the case, on the assumption that they are simply pictures representing concepts, how would you know which one was which?
What does it mean, to you, that the word "forest" must be written 森林 and not 森?
> and [there are] plenty purely phonetic characters that have no meaning by themselves ("bound morphemes").
...yes. 森 and 林 both belong to that category. But you've specifically contrasted them with it. I can't tell what you're thinking of.
Characters can be classified by origin, so that 森 is "从林从木", 切 is "从刀七声", and 下 is "指事". You seem to be reaching for this, but "bound morpheme" is a classification of the current use of the linguistic element, not of the origin of the way it's spelled.
When the Japanese imported it, they used the characters much more phonetically. They used the whole word when that worked, but the characters got assigned to the Japanese pronunciation of the word, as well as the pronunciation from the pieces of other words where that character appeared, as well as the Chinese pronunciations. Then six hundred years or so later they imported them again, by which point the characters had evolved in Chinese but not in Japanese. So its sort of phonetic, but it's a complete mess.
Not 20%, more like 90%. https://en.wikipedia.org/wiki/Chinese_character_classificati...
In Japanese at this point most kanji have an onyomi (the sound of the Chinese word, which has been adopted into Chinese the way Latin words like "adopt" are adopted into English) and at least one kunyomi (the sound of a synonymous Japanese word not derived from Chinese). This does add difficulty but it is somewhat compensated for by the smaller repertoire of characters used in Japanese. A lot of the most common Japanese words, all loanwords from languages like English, and all the inflectional suffixes are normally written with one of two purely phonetic syllabaries.
>> When the Japanese imported it, they used the characters much more phonetically.
Japanese kanji are much less phonetic than Chinese hanzi. For hanzi, you can ask "how is this character read?", and it's a simple question with a simple answer, because that question is the basis of the writing system. Kanji are assigned all kinds of different readings on the theory that what really counts is the semantics.
For example...
>> They used the whole word when that worked
Not even in the oldest Chinese writings do you see one character representing a multisyllabic word. Identifying characters with words rather than syllables is an innovation on the part of the Japanese.
Tangentially, you mentioned that the vast majority of characters are phono-semantic compounds. I've been watching some youtube videos in which Japanese people are presented with kanji of varying levels of obscurity and asked to speculate on their pronunciation. Without fail, when they don't know the answer, the interviewees speculate that the two major components of the character both contribute to its meaning.
And that always surprises me because a two-meaningful-components construction is so rare in the character system. Almost all characters aren't constructed from two meaningful elements, and I would have thought the Japanese would be familiar with that fact even though they can't understand the phonetic hints. Do you think this is more of a case of them not knowing how characters are formed ("ignorance"), or more of a case of them speculating on the meaning of each component purely because they don't have the ability to speculate about the phonetics ("searching under the lamppost")?
[Particularly where the obscure kanji are part of an obscure phrase borrowed from Chinese, speculating about the phonetics would be helpful to the problem, but I'm assuming most Japanese just plain don't know what kinds of sounds a Chinese phonetic component might be hinting at.]
I agree with your "searching under the lamppost" theory. If I'm Japanese and I see an obscure kanji, its phonetic (component) only gives me information about its onyomi, which is almost certainly some wildly obscure loanword from late medieval Chinese that isn't even in my recognition vocabulary, much less my productive vocabulary.
It might also be true that I don't know offhand the onyomi of other characters with the same phonetic—in real life I'm a native English speaker, a second-language speaker of two or three Romance languages, and the kind of person who likes to go around thinking about obscure etymological trivia, but I was today days old when it first occurred to me that "suspicious" was probably etymologically "overseeish", cognate with "perspicuous", "spectrum", "speculum", etc. (I was right about "spicious" but wrong about "sus": it's actually "uplookish".)
So it would be totally unsurprising for even a highly literate native Japanese speaker to know the onyomi of numerous characters sharing the same phonetic, but not have that shared sound come to mind when looking at a novel character with the same phonetic, even if they can guess which part is the phonetic and that the obscure word is in fact Chinese in origin. And the YouTube video is likely edited to focus on the people who got things most entertainingly wrong.
