DevOps should not be an excuse to be cowboys. Agile has the concept of the architectural runway where the architecture is rolled out just in time for the solution to work. I have always found it ironic that something "just in time" would try to use an analogy where there is so much health and safety that "just in time" is years in advance!
Anyways, this promises to be an interesting discussion given the readership of El Reg.
The problem I have with allowing Devs to decide all aspects of how something should be done is that they ignore the cost of technical debt. Six months in, when performance in the real world is poor, and the architects are finally allowed to look at the crap that was released, the Devs just claim ignorance and say that it passed the sprint demo.
The Devs then get all the credit for delivering the widget on time, and "legacy IT" gets all the blame for the last-minute costs of making it secure, performant and operationally reliable.