Less Hair
Less Hair, let me explain/elaborate a bit. At both Boeing and the FAA, there are "Specialists" and "Bureaucrats". The Specialists understand the system(s), figure out if it's working properly, and pass judgement. The Bureaucrats deal with the paperwork and associated processes. Pre-ODA, the Boeing Specialists dealt directly with the FAA Specialists (and visa-versa), then when we were both happy, we'd communicate that to our respective Bureaucrats and sign off the approprate forms, and the Bureaucrats handled the paperwork and did the actual cert. In some cases (e.g. Service Bulletins) - where the FAA had granted the appropriate delegations - as soon as I'd signed the approval form (8110-3), it was considered certified and Boeing could release it.
With ODA, the Boeing and FAA Specialists all but stopped communicating with each other. Instead the Specialists communicated with the Bureaucrats, who would then communicate with the others Bureaucrats, who would then communicate with their Specialists. Seriously! Since the Bureaucrats seldom knew anything about the subject matter, stuff got lost or muddled in translation, and things that formerly got done in hours or days suddenly started taking days or weeks. Often, in order to straighten out what the Bureaucrats had muddled, we'd have to wait for the Bureaucrats to set up a meeting between the Specialists (with the Bureaucrats in attendance to make sure they could check all their process boxes) so we could un-muddle it...
I can't speak for other groups, but within Propulsion, every AR I knew that had been a DER previously hated ODA.
Worse, as I noted, the FAA formed a new group to deal with Boeing. The FAA guy that was the focal for Propulsion - Tom - was a good guy and pretty sharp, but he was inexperienced at what some of the Propulsion disciplines did and how we did it. At one point we asked him - point blank - why so much stuff that pre-ODA had been routinely delegated was now being retained by the FAA. His response was he really didn't know what we were doing or how we tested the software! By contrast, pre-ODA, one of the FAA Specialists I routinely dealt with
had been in my group before he went to the FAA and so knew exactly how it worked. And some of the people under Tom were simply horrible - one was so bad that his name became almost a swear word - as in if you found out your cert plan had been assigned to him, you'd been "(name)ed".
Now, I'm not saying ODA was a complete mistake - there were areas where it made a lot sense - interiors comes to mind. Every single interior configuration has to be certified - just adding or deleting a row of seats means the entire interior needs to be recertified and it was a major cost and time drain. ODA was made for that. Similarly, relatively minor systems changes on a mature system. But for certifying a new aircraft or a major derivative, ODA was a disaster. I honestly don't think the MAX fiasco would have happened with the old, pre-ODA system.