Your pithy dismissal leaves out hundreds of pages of religious rites and project management dances which invariably turn into productivity-sucking meeting overload, unachievable goals, and constant product churn, effectively alienating everyone from the developer to the user, leaving only the managers satisfied. Like telling a college student that communism doesn't work, any objection is met with "well they're just not doing REAL Agile," skipping over the fact that nobody on Earth seems to be "doing REAL Agile."
Agile could just as well serve in the headline in place of DevOps.
This is not how it works in real life. Contracts are made to the lowest bidder, there are promises to keep or heads will roll.
By iteration 10, your customer is fuming that the half baked idea has more exceptions than handled scenarios and the finger pointing begins. Also, forget about architecture, performance, security and other pesky little problems. I have never seen it play out differently.
The biggest problem is that the person footing the bill does not care about your story points or retrospective- and I don't blame them for that
Agile could just as well serve in the headline in place of DevOps.