It doesn't work fine for Korean and Chinese either, we just accept it begrudgingly.
Check out the Noto Sans CJK fonts repo[1], as of now it has five variations: Japanese, Korean, Simplified Chinese, Traditional Chinese, Hong Kong. There wouldn't be a need for so many variations if Unicode works perfectly.
But Unicode is already infinitely better than what existed before, so as I said above, we just kind of accept it begrudgingly.