All languages that people speak today import new words from other languages every day. Unless you are a linguist, you probably don’t realize that all languages have “rules” (even if they aren’t written) for how to import words from foreign languages.
In the American version of English, we first try to say the word the way it is said in the foreign language (even though we often get it wrong). Then, if the foreign word is from a language that uses the same alphabet as we have, we pull in the foreign spelling too.
The result is that spoken English has more exceptions to the rules (it becomes less phonetic) every year.
So what is an alphabet really? An alphabet is just a system for writing sounds on paper. Good alphabets have a fixed set of rules and very few exceptions.
When Koreans decide to import an English word, they try to say it the way it sounds to them, but then they spell it phonetically, using the Korean alphabet. So Korean stays phonetic because it doesn’t share an alphabet with other languages.
Russian stays fairly phonetic because it only shares an alphabet (sort of) with a few highly related languages.
English is still fairly phonetic, but French has imported so many foreign words that written French is only slightly related to spoken French.
When you learn Russian or Korean, you pretty much only have to learn the spoken language, and then the written version is the same thing. When you learn French, it’s pretty much like learning two different languages.
We have a related article on why the Cyrillic alphabet makes learning Russian easier.