You don’t _need_ it but I think it’s nice to know kanji (or hanja as we say in Korean) to understand deeper cultural meanings in the language.

To give an example, I’ve just watched episode 12 of “Strange attorney Woo”, and one of the character talks about the two different hanja that make up 사 in 변호사 and 검사. A lot of the older generations still use this kind of comparison to make a point about nuance/history of a word.

But if you talk to younger generations, they talk predominantly in internet slangs and have no clues about hanja.