Short-term thinking seems to be a big factor in all these issues.

On the other hand, Airbus went ahead with the A380 and gets a lot of bad press for it ("How could they not have seen this coming").

And the 757 is an old design too.

Depends what you consider "old", but the 757 is from the same era as the A320.

A380 was an example of "spending now in hope of future return". It was a case of long-term thinking gone wrong.

You cannot avoid mistakes every now and then. At least it had no particular safety issue and is quite a reliable aircraft, and they still made money with it. This is nothing like the issues Boeing is facing.

Sadly, in the end they lost money on it. They came to a point where producing the plane was profitable, but they never recouped the development cost: https://simpleflying.com/was-the-a380-programme-profitable/

A lot of A380 development went into A350 and new techniques going in other planes.

Including 787, actually.

Obviously the 757 is in the same class as the neos, but they could never have competed with them. Either Boeing continued selling ever more efficient 737s or they risked losing the entire segment to Airbus.

Upgraded versions of the even older 737 are competing with the neos just fine, if you go by sales placements.

Well, yes, exclusively because of the type rating.