Isn’t behavioral economics a depressing view of human nature?

"YES" but that's the truth. Excellent analogy of behavioral economics - here:

"It is true that from a behavioral economics perspective we are fallible, easily confused, not that smart, and often irrational. We are more like Homer Simpson than Superman.  So from this perspective it is rather depressing.  But at the same time there is also a silver lining. There are free lunches!

Take the physical world for example. We build products that work with our physical limitations. Chairs, shoes, and cars are all designed to complement and enhance our physical capabilities. If we take some of the same lessons we’ve learned from working with our physical limitations and apply them to things that are affected by our cognitive limitations—insurance policies, retirement plans, and healthcare—we’ll be able to design more effective policies and tools, that are more useful in the world. This is the promise of behavioral economics – once we understand where we are weak or wrong we can try to fix it and build a better world.

Take again the sub-prime mortgage crisis.  Imagine that we understood how difficult it is for people to calculate the correct amount of mortgage that they should take, and instead of creating a calculator that told us the maximum that we can borrow, it helped us figure out what we should be borrowing.  I suspect that if we had this type of calculator (and if people used it) much of the sub-prime mortgage catastrophe could have been avoided.  This of course is one idea to fix one problem, and there are many ways to think about how to improve our lives along many of the decisions we make every day. This is why I think that behavioral economics is so optimistic, useful, and important for our personal life and for society."