Sounds like you company is clearly hiring the wrong MBAs, maybe the problem is your company :)
Agile is designed to get a product to a customer, rapidly and adaptively. But this is mostly useful for software that stands alone; you can't always rapidly adapt microcontrollers, bone drill burrs, heavy turbines and optical sensors. Even if you could make a 'quick hack' to one, there's 50 standards to reassess, and if one fails, you have to go back and re-do your change.
The OP is right. There are problems that require longer term, complicated solutions that have to be designed first, approved second, and implemented third. An agile MBA is not dumb; they just don't all work on the same problems.
It goes back to hiring the right people, not to the people themselves :)
I think the difference is that most engineers understand when high reliability is necessary, even if they can't deal with the pressure of implementation. An MBA whose job is to "move the ship faster" simply isn't going to understand the distinction between parts of the system that can be thrown together, and parts that absolutely can't.
Hard to hire the right people when the majority of MBA's aren't engineering undergrads.
Lately I've been flying a lot and even now, after hundreds of flights, each time the plane takes off I think about how amazing it is that this whole air-travel system works so reliably and safely. Kudos to Boeing and Airbus engineers.
I've worked in nuclear energy, surgical medical imaging devices, and in the auto industry - and it really gets me in a tizzy when a fresh "agile MBA manager" expects a "quick hack" solution to some of these problems. There just isn't always one when quality/reliability are requirements, not nice-to-haves.