A equally modern design (777) has just as little physical connection to the engine. But you pointed it out nicely: It must be the cost penalty that inhibited AI engineers to consider the backdrive depriving us of a (my interpretation) extremely useful feedback in case of screw up or confusion (as in this incident).
Hmm - your phraseology implies that it was monetary cost to Airbus I was referring to, when I was referring to cost in engineering terms, a very different meaning of the word. You should be aware that the anti-AI crowd make hay by ignoring that kind of distinction.
All the differences in implementation prove is that the engineers and pilots on the 777 project came to a different set of conclusions than their counterparts on the A320 project. No doubt both implementations have pluses and drawbacks.