If answering the question tells you what you want to know about a candidate, then it's a good interview question. If it doesn't tell you that, it's a bad question.
Easy questions like FizzBuzz do serve a specific purpose. If a candidate can't code FizzBuzz, they simply can't code and you can end the interview early. I'd rate implementing a linked list only slightly harder, but it can start a conversation about data structures in general that will reveal a lot.
Just remember that no single interview question will tell you everything you want to know. You really need to have a group of questions ready. You should ask questions in a sequence from easiest to hardest so you can find the limit of what the candidate knows. If you ask one question and they nail it, you still don't know what else they do or do not know.