Good question. First of all, there is a 'one-to-one correspondence relation' between Hangeul and Hanja while there's not between Kana and Kanji. This means that Korean sentences don't grow longer without using Hanja, 'efficiency' remains whether we use Hanja or not. Second of all, Korean sentences are written with space between grammartical elements ; the opposite to Japanese ones. So it's still easy to read. Lastly, Korean has many syllables ; Korean has 10 vowels(+11 diphthongs), and Japanese has 5 vowels(+3 diphthongs). Futhermore, every Korean consonant can function as a final consonant. For this reason, Korean homonyms are less than Japanese ones, and we easily figure out which word is Sino-Korean or not. An example in English, 'ailurophobia' (an irrational fear of cat) This word doesn't sound English, comes from the Greek, 'αἴλουροςφόβος' = αἴλουρος(cat) + φόβος (fear). If you learn phobia means 'fear', you can figure out that '-phobia'-shaped words are irrational fears of something. 1) People say 'ailurophobia' when they say they are afraid of cats, from this situation, you learn 'ailurophobia' means a fear of cats. 2) People say 'ailurophobia' when they say they are afraid of cats, you learn 'ailurophobia' means an irrational fear of cats. If you look it up in a dictionary, you learn it's made up of 'αἴλουρος'(cat) and 'φόβος'(fear). You got clear on it. The reason we learn Hanja is that it enables us to get a better understanding of every Sino-Korean word and Chinese idioms. And also we can avoid making spelling errors. We are to take Chinese literature classes in school. For Korean learners, however, I think they should learn Korean using Hangeul till their Korean nears a semi-advanced level. - If someone can't write his/her name in Hanja, they will be regarded as uneducated...surprising news unless they're kids or non-Korean.

As an alternate view... I think we manage very well using English, which shares an alphabet with most of Europe. (not counting the colonised countries of the Americas and South East Asia) ;) In the short answer: meaning is established by context. This covers both spoken and written forms in any language.

yeah, somtimes it matters since many of korean words are from chinese characters, and at the same time, many of them are homonyms with each other. but mostly, we can guess the exact meaning of the words from the context. but if there are problems with understanding, we can also use chinese characters to make it clear. and i, myself, am an advocate of learning chinese characters, as it helps learning other languages of asian countries very easy.