We don't have a model for how an LLM that doesn't exist will respond to a specific query. That's different from lacking insight at all. For an LLM that exists it's still hard to interpret but it's very clear what is actually happening. That's better than you often get with quantum physics when there's a bunch of particles and you can't even get a good answer for the math.

And even for potential LLMs, there are some pretty good extrapolations for overall answer quality based on the amount of data and the amount of training.