There is always something to learn from an accident, providing we identify relevant issues.
In complex accidents it is difficult to identify clear safety benefits of technical solutions, particularly those events involving errant human behaviour; engineering arguments often revert to 'more training' or draft another SOP.
The industry needs a measure of the effectiveness of technical interventions being able to influence human behaviour; this cannot be absolute, only a judgement.
Stick shakers have demonstrated a high level of effectiveness. The 146 was particularly good because the stick was mounted on the 'floating' cockpit floor, so there was an enhanced effect which alerted pilots when the autos were engaged (although IIRC the 146 autos disengaged at Vss).
It would be interesting to investigate the effectiveness of floor or seat mounted shakers in sidestick aircraft for improving awareness and stall avoidance.
Thinking further afield, some notable stall accidents involved generic issues related to the operators training. Colgan had recently focussed on tail stall (requiring the crew to pull up), which was not applicable to the type. The A330 required refresher training for loss of airspeed, where memory items required an initial high nose attitude, which did not apply in the cruise.
As discussed previously, closer monitoring of training practices might help, so too an understanding of why regulators believed that these training programmes were necessary.
Much of what has been discussed and done for safety improvement focuses on a single event which rarely applies across the industry or for future 'unforeseeable' events; we tend to fix the last problem and overlook generic items because it is difficult to agree on the judgement of their projected effectiveness.