I actually think Martin Armstrong hit the nail on the head when he said that the 2008 recession was precipitated by a transition from relationship banking to contractual banking. What he means by that is that when a bank used to loan you money, they kept the mortgage contract themselves, and so had huge incentive to vet you properly. In the decade preceding 2008, that model went out the window. They now had an incentive to sign up as many people as possible for the loans because they no longer had to keep the contract. They could package it up into derivatives and pawn it off on some poor schmuck that you've obscured the risk from. No need to vet anyone, because you could sell the contract as soon as you made it, and collect all of the value while only holding the risk for a very brief time. The lifting of Glass-Steagall made this possible.
In a world without other financial regulations, a lack of Glass-Steagall wouldn't be an issue, because people would be incented to properly assess risks and structure investments accordingly, but under the current system, lifting Glass-Steagall and allowing banks to gamble with people's deposits while propping them up with government money is a huge part of the problem. And this problem has gotten bigger in the interim.