Agree on most points. However as someone who has worked on new aircraft I can tell you that friction/mis-communication/finger-pointing between airframe and powerplant manufacturer is a huge issue. There is a common saying in the industry, that you should never design a new airframe and a new powerplant at the same time. Each new aircraft certification program should be one or the other

Sure, as there is when any two companies work together but to say they have no ability to communicate performance parameters, that they have no ability to work together, is just wrong.