But it thinks just great on stuff it wasn't trained on.

I give it code I wrote that is not in its training data, using new concepts I've come up with in an academic paper I'm writing, and ask it to extend the code in a certain way in accordance with those concepts, and it does a great job.

This isn't regurgitation. Even if a lot of LLM usage is, the whole point is that it does fantastically with stuff that is brand new too. It's genuinely creating new, valuable stuff it's never seen before. Assembling it in ways that require thinking.

Creating complex Excel spreadsheet structures comes to mind, I just did that earlier today - and with plain GPT-5, not even -Thinking. Sure, maybe the Excel formulas themselves are a "98% match" to training data, but it takes real cognition (or whatever you want to call it) to figure out which ones to use and how to use them appropriately for a given situation, and how to structure the spreadsheet etc.