Most of the behavioral economists I know would argue that behavioral economics is a supplement, not a replacement for traditional economics thinking. The argument is not the traditional economics gets everything wrong, but that it gets some things wrong and that supplementing it with behavioral work can help get some of those things right. Some of the insights discussed at the course, such as Esther Duflo's comments about hope, or Sendhil's discussions of the importance of reminders and salience, can clearly be used to tailor micro development interventions to improve take-up and help the poor save and invest more. Exactly how we use it to solve some of the government failure questions is, I believe, more challenging. Shanta's "Concluding Remarks" video, linked here, does a nice job of summing up this point: Let's not throw the traditional economics baby out with the bathwater.