Traditional Keynesian models, like the IS-LM one, were discarded as they lack micro-foundations. They were also subject to the Lucas critique (in the sense that one cannot properly estimate a macroeconomic model if the parameters respond to changes in monetary/fiscal policy).
Explaining the crises (not all, but many of them) as being liquidity traps is not only a misinterpretation but it also leads to false solutions. Just look at the case of Japan after two decades of “policy experiments”. (New) Keynesians like Krugman have reduced its stagnation problem to a liquidity trap and prescribed a wrong therapy which in the end failed to lead to real economic growth. But probably the case of Japan deserves a separate discussion.
The last global recession raised concerns about the ability of macroeconomists to predict crises of such magnitude. Certainly, the forecasting is not the main focus of macroeconomics. I would say that, at least nowadays, it is of rather marginal interest to academic macroeconomists. A proof in this sense is provided by the very low number of publications related to macroeconomic forecasting.
Some of the most prominent economists believe that inflation is a solution to the economic woes of US and Euro Area, and I particularly mean Krugman and DeLong. But is it so?
The sovereign debt crisis, see also my blog post on the sovereign debt crisis that focused on deficit spending, has made more evident than ever that the Euro Area is deficient in many respects and one could reasonable state that it is far from an optimal currency area.
There is a general agreement that the mainstream macroeconomics has largely failed to predict or correctly estimate the last economic and financial crisis, see the introduction here on the website of the Institute for New Economic Thinking. This failure has motivated more than ever different heterodox approaches to macroeconomics.