What have policy makers learned from the 2008 financial crisis?

There's no doubt that investors have been forced to move up the risk curve in search of yield amid the Fed's easy money policy. But with tightening, when will investors feel the need to move back down? Can policymakers actively force this move or merely respond to market conditions? What have policy makers learned?

Mohamed El-Erian discusses regulators, banks, and the financial crisis in a solid article for Financial News: https://www.fnlondon.com/articles/el-erian-the-lost-lesson-of-the-financial-crisis-20170818?