> Can you elaborate on it? I'd love to get some more detailed information if only to facilitate my own deep diving.

To appreciate non-binariness of the problem, just try to find the pictures of different flight envelopes under different flight conditions for different planes and compare them. The wrongness in claiming that every plane can be qualified with just "has x" or "hasn't" is then more than obvious.

Then imagine that you'd actually need the response diagrams -- some valid measurement of how the plane reacts to the controls. That is the actual point of problem: exactly how the curves look like, where are which limits between "fine" and "deadly" and how dangerous is which kind of movement or non-movement of which control.

Then consider that Boeing even after the first crash claimed that "everything's fine" in their "additional instructions" which were followed by the Ethiopian air pilots but that then the plane responses were such that the pilots were practically helpless: the plane "didn't listen." That's what's happening with the positive feedbacks, and that is what "nose up" behavior is -- but the answer is not "yes-no" but where and how much in every point.

The helplessness (or not) of the pilots (i.e. how much of their force produces how much of the outcome under which conditions) is also something that can be plainly measured and drawn.

I don't have the corresponding (complex) pictures of Boeing 737 MAX flying without the MCAS. And I don't think they are available at the moment. But that is the point. Who are those who claim that they know it's safe and what is the basis of their claim? We have already plain demonstration that Boeing openly lied with their "everything's fine" claims -- I can't imagine that nobody inside of a company that is supposed to sell the planes orders of which measure hundreds of billions of dollars has such pictures.

But who can say simple "it's safe" when to be able to really claim it somebody has to evaluate these complex aspects demonstrated by the diagrams and not just construct a simple "yes-or-no-is-it-kinda-same-as-this-other-thing" question?

Reducing that whole topic to such kind of argument "well 727 was bad too" is obviously misleading. The way I still see it is: had it been it actually safe to fly it without a functioning MCAS, there would be no "regulatory requirement" to put it there at all. The "requirement" was an actual "it's not safe without it." But the way that "requirement" looked like was also not "yes no" but "see this diagrams -- the plane should approximately behave so and not the opposite of that." And the opposite is the characteristic of the positive feedback loops. MCAS was there to polish one resulting from the design driven by the marketing goal, not by physics.

Imagine when you would move the steering wheel to make a slight turn and when the car would "listen to you" under e.g. 30 mph but respond in turning you much out of the road when the speed is higher. "Well you should be trained not to try to turn the wheel when over 35 mph" "Really?" "Yes you see that other old car also responded kinda like this one, yes that old one couldn't have killed you so easily, yes, this one will, but don't worry that's actually the same, trust me, because I'm the one making and selling you this new car." "..." That's not how the sameness is compared.