In the movie "The Big Short," Steve Carell plays a slightly altered version of me. In real life, I am a portfolio manager and financial services analyst who over a 25-year career has, at times, been highly critical of bank behavior. More than eight years after the financial crisis, many people say that the large banks still pose a threat to the economy and should be broken up. Such a view captures the justifiable anger many Americans still feel toward the large banks. But I don't agree. Breaking up the banks would ignore the significant progress made by regulators to...