I once saw an old YouTube video that claimed that some hanzi are super obscure and even native Chinese have to look them up sometimes when wanting to use them, and gave the example of "sneeze".
I asked my Shanghai born coworker, who led the local Chinese friendship society, about this, and he furrowed his brow and said "...shit, actually, yeah, I'd need to look that up myself."
This is merely one anecdote, of course,
There's information density, but there's also information accessibility. And the trick is finding the balance between the two.
Having 8000 characters (in simplified Chinese) may be information dense, but how accessible is that information? E.g., a typical Chinese university graduate will know, on average, 3 -4K of them, and no doubt ones that are unused will atrophy over the years.
The balance between density and accessibility is always ongoing. E.g., I find reading presentation slides with a transcript far more information dense than watching a video of that presentation, but some people find it far more accessible in video form. And then for complex discussions, I find video calls far more information dense than Slack message or email exchanges.
In addition, if you're reading a text and you come across an uncommon character, you can often figure it out, both from context and by recognizing elements in the character (which give hints about the pronunciation and meaning).
喷嚏 is the example always used because it describes a common thing that is rarely written about, and there is no other, more frequently written character with the 疐 component that could remind people how to write it. So when handwriting, one might substitute 喷㖷 instead.
Most obscure characters are simply obscure because they refer to an obscure thing, like not being able to spell the name of a village you've never heard of.
And characters for non-obscure things made of obscure components are usually common enough that people get enough practice writing them. E.g. 藏 "store/hide" contains 臧, an archaic term for "good" that now mostly occurs in ancient idioms and as a rare surname. But hardly anybody seems to have trouble writing 藏.
Isn't that also the case in other languages? Most people don't know all the words in a dictionary for example, and a word is roughly analogous to a character in Chinese.
jˈɛs, ˈɪŋɡlɪʃ ɪz ɐ tˈɛɹɪbəl ɹˈɪtən lˈaŋɡwɪdʒ. ɪn ɐ sˈeɪn wˈɜːld wiː wʊdhɐv mˈuːvd tʊ ˌaɪpˌiːˈeɪ ɐ lˈɒŋ tˈaɪm ɐɡˈəʊ.
We all agree that English spelling is a royal pain in the ass.
Imagine a common "Germanic" or "Roman" script that would be comprehensible to any literate person that speaks any Germanic or Roman language. So the same book could be read by people in San Francisco, Berlin, Oslo and Amsterdam without the need to learn any new language.
This might be one of the reasons why China is still one country with one central bureaucracy, which is nigh impossible to establish in Europe, all the EU-wide initiatives notwithstanding.
But it comes with a high bar to clear as to what "literacy" even means. Westerners are fully literate in their native languages after several years of elementary school; the same cannot be said about the Chinese.
Kanji is part of the Japanese writing system, it's not the entire thing. "Translated to Japanese kanji" is like saying "translated to English consonants".
> Kanji characters were printed significantly larger than ASCII, so that accounted for a lot of it.
Japanese books also have a lot more whitespace and are generally smaller than western books. I disagree that the font is much larger -- the books I read have a font size that is practically identical to most western books (the difference is that CJK characters are more boxy and so they may appear larger).
> ASCII can have a pretty small font and still be perfectly legible - apparently not so with Kanji.
You can print kanji pretty small and have it still them be legible to native speakers (just look at the first video games that used kanji instead of just using kana -- the effective font size is tiny).
The hiragana and katakana are syllabaries and don’t have the information density that you get with kanji.
I don’t imagine you’d get Japanese books that are more compact than their English counterparts because per sentence Japanese texts are comprised mostly of hiragana and katakana with a sprinkling of kanji.
Chinese on the other hand is all hanzi, and that does provide significant information density.
I used to have the lord of the rings in both English and Chinese on my bookshelf. The 3 volumes in Chinese where about the same thickness as a single volume in English (width and height were approximately the same) and this was with a much larger Chinese font required for legibility.