[caminmccluskey]

Totally agree that a valid approach is looking at what should exist. I also agree that the issue with that is that your conception of what should exist needs to be grounded in reality. Ensuring you're focused on problems is that "contact with reality".

To that end, I would contend the examples you give are absolutely founders that wanted to solve a problem (or realised very acutely that they were solving a problem as they built something new)

Facebook's core problem was figuring out if that person you met at a party was single without being creepy. A problem that Instagram now solves much better (coincidental acquisition? I don't think so).

The 2 Steves initially met and solved the problem of long distance phone charges by building legally questionable "blue boxes" - https://en.wikipedia.org/wiki/Blue_box. They later united on the problem of bringing computers, which they had a passion for and knowledge of, into the homes of everyone.

Amazon is an interesting point - Bezos saw the clear trend of increasing internet usage and realised there needed to be commerce online. He was certainly smart about the type of things that could sell well on the early internet. I would argue it solved a problem - long tail commerce (i.e. bookstores can't stock books about any conceivable topic) - but I'd concede that perhaps wasn't the primary initial motivation.