If the "people" part of economics invalidates all of its assumptions and models, then how useful is it really? Everything beyond intro micro and macro is as pie in the sky as string theory, and motivated academics are also similarly keen to keep that PhD research money hole absorbing all the resources it possibly can.

> Everything beyond intro micro and macro is as pie in the sky as string theory,

That's kind of backward: intro micro and intro macro are the areas of economics most tied to abstract assumptions which are neither grounded in nor consistent with empirical observation (excluding, of course, both work addressing things like hypothetical optimizations and work in overtly ideological rather than empirical approaches to economics, like that of the Austrian school, but neither of those even aspire to describing status quo reality.)

The 'people' part of economics has evolved into what is called behavioral economics. Traditional economics assumes that people will make the ration choice, but that can be a pretty limiting view of the world since people obviously are not always rational. I don't disagree that traditional models and assumptions are not that useful when applied to the real world.