Insightful vs. Rude: “一语道破” is about clarity and wisdom, not tactlessness. While the truth it reveals might be uncomfortable, the focus is on the brilliant perception of the speaker. It's different from just being blunt or rude for the sake of it. A term like
直言不讳 (zhí yán bù huì) focuses more on the speaker's frankness, which could be perceived as either refreshing or tactless depending on the context. “一语道破” is almost always a compliment about intelligence.