On whole failure of the goal. Change a plane in big way, but try to get it act like it did not change. To avoid explaining and training pilots. So instead of training pilots to expect plane to act certain way in certain scenarios, it was instead fixed in software and hardware. But well that combination was done poorly and it should have still been explained.

They're not solely responsible, but they are responsible.

If they fulfilled the requirements provided to them I don’t see how that could be the case. Even if they didn’t it was Boeing’s job to verify that.

It’s a bit like blaming low level construction workers for a bridge that collapsed (assuming they didn’t sabotage anything on purpose).

You should always question if the requirements you get make sense.

And? How would that help if they have no clue about how that specific system was supposed to work?

You find out. Doubly so if you're working on safety critical systems like an airplane