I'm interpreting "brainstorming" to be any kind of general noodling on an issue to try to find new/novel/interesting solutions. In that case, I think every significant moment of true inspiration I had (of which there have been like, maybe 3 ever), they were always the result of seemingly random, completely unrelated things popping into my mind that, for whatever reason, clicked perfectly into the problem I was mulling over. To me, this means that manufacturing "true" inspiration doesn't require a tool that can deviate from "standard" human thinking patterns. I think it just means that you would want a tool that helps expose you to as many new and unknown fields/concepts/ideas in as little time as possible. So I think in that way LLMs are an amazing tool for helping one to brainstorm.