I think there's too many red flags there to chalk it up to a single problem: time-consuming conversations, rigid abstractions, resistance to changes, demanding

I think there's too many red flags there to chalk it up to a single problem: time-consuming conversations, rigid abstractions, resistance to changes, demanding PMs, total overhauls needed, more bureaucracy on change approval, you also complained about fixation on code quality. Saying that it's all up to the one single difference even though there's so many ancillary issues screams of "I've found a silver bullet syndrome" to me.