>It’s a reason planes basically look the same for many decades too; newer stuff is harder to get through.
Not true. The reason planes look the same is because that's simply the optimal shape and layout, aerodynamically, for carrying passengers in the most fuel-efficient manner. Ask any aerospace engineer.
But there's been some big differences if you look more closely. Engine nacelles are a lot larger than they were 50 years ago, since bigger high-bypass turbofans are more efficient. And winglets are basically standard now. Under the skin there's huge differences: fly-by-wire, composite wings, etc.
>Also part of why Boeing thought it best to revise an existing design once more
Wrong. It's because some customers (cough Southwest cough) would only fly 737s, and because the FAA's broken rules allowed anything called a "737" with a 737 airframe to be flown by any pilot rated for that aircraft, even if they've only flown one from 1969, even though there's big differences between the generations, and because the FAA didn't mandate a more thorough process for this loophole. Boeing was afraid that these 737 users would buy the A320neo instead of a different Boeing plane, if forced into a choice of something new. In reality, the 737 airframe is old and obsolete, and should have been retired ages ago, but is only kept alive because of bad FAA regulations.
>The process led to bad design decisions quite directly, though of course everyone blames Boeing (rightly) but not the process the FAA imposed.
This is correct. The FAA is the root of the problem here. But the problem isn't that "processes can be gamed around", the problem is that this particular regulatory agency was corrupt and failed in its primary duty. Of course regulations can be gamed around; that's why the regulators are supposed to stay on top of that, and continually revise regulations to deal with this. It's a cat-and-mouse game, but here the cat just gave up and let the mouse tell it how to do its job as a cat. The answer to this problem isn't to get rid of cats; it's to euthanize this particular cat and get a better cat.