If everyone is competing to be THE notes app, and there is an expectation for every person in the entire world to use said Notes apps for nearly all tasks in the future? Yea, it absolutely could deserve a global investment of roughly just 3% U.S. GDP. Moreover, isn’t it up to the people investing to decide that, rather than people who used ChatGPT once and then complained on the internet?
No, it absolutely wouldn't justify that level of investment and if that was happening we'd have hacker news articles rightly calling the notes app bubble.
No, because to replace a notes app you need pen and paper. But to replace LLM you need at least a human. There's literally nothing else. And humans don't come cheap.