I also used it for advice on a massive personal decision, but I specifically asked it to debate with me and persuade me of the other side. I specifically prompted it for things I am not thinking about, or ways I could be wrong.

It was extremely good at the other side too. You just have to ask. I can imagine most people don't try this, but LLMs literally just do what you ask them to. And they're extremely good and weighing both sides if that's what you specifically want.

So who's fault is it if you only ask for one side, or if the LLM is too sycophantic? I'm not sure it's the LLMs fault actually.