Korea has abolished kanji and replaced it with hangul, a completely phonetic alphabet.
It is possible to write Japanese using only hiragana and putting space between the words, but because of the large number of homophones (words with same pronunciation but different meaning) it would be very difficult to understand.
But there are advantages to kanji.
With kanji, it is possible to write very long and complex sentences in a very simple and concise way. A literal English translation of a Chinese or Japanese text is usually much longer and verbose.
Because kanjis are basically drawings that represent meaning instead of sound, they are more resistant to the test of time. It is possible to read texts in kanji written thousands of years ago. Even though we may not know how ancient Chinese pronounced the words, we can still read and understand what they wrote, because each kanji shows meaning, not sound.
In comparison, it is very difficult to understand text in English written a mere hundreds of years ago. Because pronunciation changes incredibly fast. You can see changes in pronunciation in just a few decades. All phonetic languages in the world are doomed to disappear in just a few hundred years, exactly because pronunciation changes too fast.
Latin has disappeared. Spanish and Portuguese used to be the same language. How long will it take for American and British English to become different languages?
Probably Chinese will be the only language to survive thousands of years from now.
Chinese is one of the simplest, oldest, most spoken languages in the world.
I have heard some people say that Chinese is the most advanced language in the world.
One of the reasons is that Chinese is not phonetic. Kanji doesn't represent sound, it represents meaning. The sound may change, but the meaning usually doesn't change much.
Millions of years from now, when humanity is long gone and an alien species visits the planet Earth and finds the books written by humans, it is possible they may be able to decipher Chinese, and only Chinese. Because kanji conveys meaning directly, not sound.
Trying to decipher a text in English may be impossible, because you want to know the meaning of the words, not how they are pronounced.
Chinese may be the only language to survive and tell the history of mankind, all because of kanji.
How to send a message to the future, a message that human beings can read and understand thousands of years from now?
How to send a message to an alien species?
How to communicate with animals?
How to write a message that is understandable and decipharable by any other human being?
Can you write in English? No, because English is a phonetic language. Even though it is not as phonetic as Portuguese, Spanish or German, English probably was once as phonetic as those languages. By phonetic I mean that the written words are meant to represent sounds. This kind of representation is extremely powerful. With only 26 letters you can write down any word in the language.
But there is a problem with phonetic languages: pronunciation changes too fast. You have to change the way words are written in order to keep up with the changes in pronunciation. It means that books get obsolete too fast. It is difficult to read and understand books written hundreds of years ago. If you took a time machine and went back to the Middle Ages England, it would be almost impossible to understand what they were saying. The spoken and written languages changes too fast.
So if you wrote down a message in English, it would be practically impossible for people thousands of years in the future to understand you. The English language itself will inevitably change, transform, disapppear, become a different language entirely.
And nobody in the future would be able to understand your message.
So you cannot use a phonetic language to write down a message.
You have to use a pictographic language like Chinese.
Chinese is written in kanji, which are pictographs or ideograms, a written symbol that represents an idea or object directly rather than a speech sound.
Since ideograms are not meant to represent sounds, they are immune to changes in pronunciation. No matter how much the spoken language changes, there is no need to change the written language. It is possible to read and understand books in Chinese written thousands of years ago.
The idea of using ideograms is not new.
The Arecibo message uses them to communicate with aliens.
Pictures are used to communicate with animals.