The basic issue as I understood from the news (Biggest I’ve flown is a C172 and those the yokes are mechanically connected) the problem was there was no tactile feedback “pushing back” against the stick when the other stick was being used. I gathered from news at the time that the Boeing aircraft indeed did have this feedback, but of course I don’t know. It seems a fairly elementary safety measure?
For mechanical systems like yokes, they’re mechanically connected. The details of a Boeing and Cessna differ, but it’s still metal rods, bike chains, and taught cables, connecting the two yokes somehow.
FBW was more or less invented for the F-16 program. The prototype sidesticks did not move at all. It was a 100% rigid handle that sensed the force applied by the pilot’s hand/arm. That proved to be difficult to fly smoothly & fatiguing as well. Part of the point of FBW as applied to fighters was that if you wanted max-effort turning, just yank back to the stop and the computer would manage the elevator / stabilator deflection to produce max Gs with no stalling if slow nor over-Ging if fast. Same thing for max-effort roll-rate: just go hard left or right on the stick and the computer ensures you don’t throw the airplane out of control.
Problem was with a non-moving stick there was no “stop”. Test pilots were wearing there arms out pulling with e.g. 150lb of force when only 70# was already max command.
So before the F-16 went into production they replaced the non-moving stick with one that had abut 1/8" of travel in all 4 directions. And of course very stiff springing so it took the full e.g. 70# of aft stick force to hit the stop. But at least pilots could feel the difference between “I’ve pulled to the stop” and “I’ve pulled partway and there’s more if I need it.”
That was state of the art when the A320 was being designed. They designed a stick with more travel (~1/4 - 3/8"), and softer springing since max effort control deflection is generally very rare in airline ops, despite being routine in fighters.
And that’s where all Airbus products are today. The lack of force feedback between the two sticks (so-called “haptic feedback”) is seen as an idiosyncrasy, not a problem needing fixing. Certainly not a problem needing mass retrofitting to 40 years’ worth of existing in-service airframes on A320, A330, A340, A350, and A380. And now the A220 formerly Bombardier C-series.
Sticks with force feedback AKA haptic sidesticks are now used in a few bizjets. There doesn’t seem to be much of a reaction either way. It sounds like it’d be helpful, but folks using them aren’t hailing it as a revolutionary improvement in safety or usability.
It’s worth mentioning that in older USAF fighters & fighter-like aircraft with mechanical control sticks and fore-aft seating, such as T-38, F-5, F-84, F-100, F-101, F-4, and F-15, planes have occasionally been lost due to confusion about who is flying the airplane. Whether it was two pilots fighting each other over the controls, or zero pilots flying and both thinking the other pilot and airplane is going nuts. This with moving sticks that move a hell of a lot more than the little wiggles or buzzes from the fancy new haptic sidesticks.
The real issue with AF447 was simply massive confusion and no small element of panic in the cockpit at 0-stupid-thirty in the wee hours on a dark and stormy night. A haptic sidestick might have helped dispel some of the confusion, but might not have. No way to know.