Only if your career is related to the engineering/IT/whatever professional certificate required field.
There are certain fields that your skills on your work really are veiled by your English skills.
You know what you know exactly. Yet you can’t show your people that you know, by lack of communication skills.
The nuances of each of sentence you are speaking is important. Same words and sentences, but sometimes you convey different meanings. You also need to care to speak at reasonable pace as well, otherwise the audience might miss the things that you wanted to express. And this is critical on, those who majored in not IT/engineering field.
Enough? It’s never enough, and ever be. We have our limits, we know them, yet I believe I should not stop trying, because I’m living in U.S., not in Korea in U.S.