Go to any Mongolian web page and try to read it. Do you understand it? Still, it's written in Cyrillics. So how come you don't understand it!?!
Seriously now - the ability to understand a text depends on knowing the
language, not the
alphabet. This is why you may be able to read out loud a page written in Mongolian, but you won't have any clue about its content.
Likewise, I can easily read a page in Turkish or Gaelic but that doesn't mean I can also understand what it says.
What you believe to be a "major advantage" is actually insignificant for any practical purposes. And even Bernard Shaw wrote his plays in English, with the spelling he seemed to hate.
Why didn't he use a "rational" spelling instead?
Because he wanted people to be able to
understand what he had written. If people can understand, that is all that matters. This is why Chinese writing still exists: a person speaking Mandarin cannot
talk to a person
speaking Cantonese but they can communicate in writing easily.
Technically you could learn the Chinese writing and communicate in writing with somebody speaking Cantonese or Mandarin without also learning to
speak any to those languages.
If China would have conquered Europe in the 1500s (say by landing a fleet similar to that of Zheng He's in Portugal or in Egypt and conquering everything starting from there) then each European language would have still existed today. A Swede would still not be able to talk to a Serb, but they would be reading the same newspaper, written in Chinese.
Communicating in writing and communicating in speech are two very distinct things. They even use very distinct parts of the brain. So "improvements" in writing do not help much.
It even turns out it is faster to learn a language by speaking it without knowing how to write it. Only after we master the spoken language it is safe to learn how to write in it.
Could you explain what is wrong with the Chinese writing? Other that
foreigners need to make the same effort to learn it as the locals do?