An LLM is a lossy encyclopedia

Yes, LLM is a lossy encyclopedia with a human-language answering interface. This has some benefits, mostly in terms of convenience. You don't have to browse or read through so many pages of a real encyclopedia to get a quick answer. However, there is also a clear downside. Currently, LLM is unable to judge if your question is formulated incorrectly or if your question opens up more questions that should be answered first. It always jumps to answering something. A real human would assess the questioner first and usually ask for more details before answering. I feel this is the predominant reason why LLM answers feel so dumb at times. It never asks for clarification.

I don't think that's universally true with the new models - I've seen Claude 4 and GPT-5 ask for clarification on questions with obvious gaps.

With GPT-5 I sometimes see it spot a question that needs clarifying in its thinking trace, then pick the most likely answer, then spit out an answer later that says "assuming you meant X ..." - I've even had it provide an answer in two sections for each branch of a clear ambiguity.

GPT-5 is seriously annoying. It asks not just one but multiple clarifying questions, while I just want my answer.