A jackscrew is getting about as simple as a mechanical motion device can be. It should be failsafe in day-to-day operations as long as it is lubricated and inspected properly.

If it was NDT'ed for manufacturing defects, is lubed and in wear spec before flight, it is almost inconceivable that it could fail under design loads.

By failure, I mean allow the stab to flop around without restraint. A motor failure or mechanical jam should normally just cause the trim to be stuck in that position...not catastrophic. I think there may have also been a restraining strap on that design which snapped under the sudden force of failure, but I may be mixing my airplanes up.

Any alternative mechanism involving say hydraulics or gear boxes would be complicated and more likely to fail, and would need a separate brake/locking mechanism to hold the thing in position if the mechanism let go. The jackscrew, in addition to being simple, has the benefit of being self-locking once the motive power is removed.

I think that if the AK crew had stopped monkeying with the trim and landed immediately, the jackscrew would have held together long enough to get them on the ground. Of course they had no way of knowing that, but I think that accident has spring-loaded most of us to declare and put the thing on the ground at the first hint of primary flight control abnormality.