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gwern comments on Valuable economics knowledge available, ironically, for free - Less Wrong
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Name three.
Contemporary Japan, and America; the Great Depression; business cycles in general.
(I threw in a fourth one for free because I love the 'name three' heuristic even if you chose a really bad topic to use it in.)
Lumifer said (1) the state macroeconomics as a whole is bad, (2) what you learn in a principles course is not how the world actually works, and (3) macro models have huge problems dealing with the real world. These are extreme claims, and I think I was justified in calling him on them.
To your examples -- the AD-AS model (or IS-LM in older textbooks) can be used to think about business cycles in general, and the liquidity trap in particular, which covers most of your examples. The Great Depression needs discussion of monetary policy (gold standard, Friedman-Schwartz, etc), and all of your examples need some discussion of financial crises, banking panics, and asset bubbles. Japan is not that mysterious once you consider demographics and per-capita growth rates.
A good principles class will spend quite a bit of time talking about each of your examples, and show how to think about them using the standard tools.
You demanded examples where macro does not work well in the real world. I named 4: Japan remains a mystery to macro, and 'Abenomics' hasn't helped eluicidate it; the US crash was unexpected and falsified the 'Great Moderation', casting doubt on the entire structure of macro that didn't predict it; the Great Depression is only partially understood even if a lot of people think Friedman cracked it; and business cycles remain mysterious with panics and bubbles being not explanations but excuses. The growing influence of the macro views of Scott Sumner, who was a marginal figure at best a few years ago, offers another practical bit of evidence that macro is far from a settled science when it comes to contemporary economies.
I'm sure it would. Doesn't mean it is right or that macro has a consensus view on each such as how to fix and prevent and predict them.
I demanded examples of models taught to undergrads that have "huge problems dealing with the real world." The same poster went on to say that these models are so dangerously wrong one must be intellectually inoculated against them!
You've given several examples where our knowledge is incomplete. I agree! And I hope that any economist would explicitly say that there's no settled explanation for the Great Depression, or the Great Recession, or Japan's Lost Decade. But that is quite different from saying that the models we DO teach have "huge problems dealing with the real world" and "are NOT how the world works". I think the basic models ARE effective tools for understanding how the world works, and a good teacher will explain both their uses and their limitations.
In brief, the fact that there are things we don't know does not mean that what we do know is wrong, and a good principles class should teach both what we know, and what we don't.
If the state of the art cutting edge economic research is that "there's no settled explanation" for Japan's Lost Decades (plural, since we're well into multiple decades, I think), then how on earth could the simple models taught to undergraduates not have "huge problems" dealing with these "real world" events?
I don't see how this follows.
Suppose we teach a theory that says things in set X can be caused by things in set Y={A,B,C}. Then I say "there's substantial argument about whether major event x in X was caused by A or by B."
This does not mean the theory has "huge problems" dealing with real world events! It just lacks the power to distinguish between causes from within the set Y.
In the same way, economists argue about the causes of things like the Great Depression, Lost Decade, and Great Recession, but they mostly agree about the sort of causes they need to consider, and they have a common framework to think about them in (or at worst a few competing frameworks).
Then it's not a theory capable of explaining the event at all. If all you can do is throw together a variety of heterogenous contradictory theories, you haven't explained an event.
I'm reminded of Wittgenstein, now, on family resemblances - of course one could define "a game" as an indefinitely long disjunction of possibilities "a game is anything which is either Backgammon OR chess OR go OR Halo OR tossing a ball OR soccer..." but having giving this disjunction, in what sense has one actually conveyed what a game is? Same thing here.
I believe that however we explain the Lost Decades, it will involve materialism and not souls. Do I have a perfectly satisfactory theory capable of explaining the Lost Decades? No, of course not.
Are you really claiming that a theory that restricts the possible causes of an event to three has not explained the event "at all"?
Under this definition, I agree that undergraduate macroeconomics cannot explain the real world. But surely this is a rather restrictive standard for "explanation"?
I would rather say that a theory that allows us to concentrate a lot of probability mass on Y upon observing an element in X, or to concentrate a lot of probability mass on X after observing an element in Y, is doing quite a bit of explanatory work!
This isn't a case of 1 theory which predict the cause as being 3 different possible causes. We're talking 3 entire competing paradigms, and then yeah, pretty much. "We think you're sick either because people get cancer, or they have 4 bodily humors which get imbalanced, or it's all due to malignant airs. We doctors haven't figured out which is the right paradigm, but rest assured as you die: probably one of the 3 paradigms is right!" I sure as heck wouldn't go around saying "medicine has it all figured out".
So. As I said originally: macro cannot agree on an explanation for any of the events I listed, and my examples fit your demand for examples.