My understanding is that the airframe wasn't unstable in a way that's particularly unusual for commercial aircraft, and these sorts of things are regularly hand

My understanding is that the airframe wasn't unstable in a way that's particularly unusual for commercial aircraft, and these sorts of things are regularly handled just fine with pilot training. The problem was that it was unstable in a way that wasn't exactly like previous 737 models. Except actually that probably wasn't a problem so much as an annoyance. The problem was that, since retraining pilots for the MAX's quirks would have been unpalatable for customers, they decided to try and use software to sweep it under the carpet. Except perhaps the even more fundamental problem was that the FAA was so deeply asleep on their post that this glaring snow job apparently flew past them without notice.