They might be, but fly by wire does not imply that.
For the record, I don't believe Airbus plans are unstable in the way the MAX is, whose instability, from what I understand, came about because they were trying to fit larger engines on the original 737 frame (to prevent pilot retraining), and so had to move the wings higher.
Something like an F-16 however is less stable and requires constant adjustment of flaps etc. there dynamic properties of air to air dogfight are more important.
A quick google search seemed to imply most unstable airframes were military or experimental, not commercial. Unstable airframes are not appropriate for commercial airliners unless you can point to a good reason. "We don't want to train pilots" is a bad reason. The FAA should have pushed back very hard on this point.
Personally I think the flaws in the 737-MAX design process were so deep that it would be safest to just scrap the plane. It's not that the issues cannot be fixed, but rather that we'd be better off starting over from scratch knowing that good design principles will be followed the whole time.
At high thrust, slow speed, high aoa it is a little too close to neutrally statically stable.
C f. to airliners that can break up from dynamic yaw instability if the yaw dampers fail in some flight regimes.
"It highlighted the role of the co-pilot in stalling the aircraft while the flight computer was under alternate law at high altitude. This "simple but persistent" human error was given as the most direct cause of this accident"
Unstable flight profiles are not foreign in aircraft, and requiring computer systems to maintain stable flight is nothing new.
The problem is entirely how this specific system was implemented... and that can be fixed.