I'll give an example here of how Chinese characters reflect speech more than they reflect meaning-as-such. Many more examples are possible. How you might write the conversation
"Does he know how to speak Mandarin?
"No, he doesn't."
in Modern Standard Chinese characters contrasts with how you would write
"Does he know how to speak Cantonese?
in the Chinese characters used to write Cantonese. As will readily appear even to readers who don't know Chinese characters, many more words than "Mandarin" and "Cantonese" differ between those sentences in Chinese characters.
Again, I invite you to look at
to see why that is not quite true. A newer book,
is very good for explaining the neurological reasons why NO writing system could possibly operate that way.
To say that Chinese characters unify a nation of high illiteracy whose citizens in many cases cannot converse with one another in person or on the telephone
is much like saying that writing in Latin unifies the continent of Europe by providing a common means of communication among scholars from Basque Country to Finland. Each statement is about equally true, and each is about equally irrelevant to current language policy.
I already mentioned above that I have seen counterexamples--written Chinese that was incomprehensible to many of the people who might reasonably be expected to read it--in several daily life situations in various parts of China.
Korean, Japanese, Vietnamese can read Chinese text in their own languages.
No, strictly speaking they were reading Chinese text in Chinese (possibly with mind's-ear pronunciation of the Chinese characters reflecting influence from their native languages), which they acquired as a second language while learning literacy. The full details to respond to the point of view you have put forth can be found in
(P.S. I can read some current Japanese too, and of course current Japanese writing shows plainly that Japanese is a very different language from Chinese, as you correctly note. I had occasion recently to read a brush painting of bamboo with some Chinese characters on it hanging in the office of a physician, who is a man of Korean-Japanese heritage. We could both sight-translate the Chinese characters into English. I didn't ask him on that occasion how he would pronounce them.)