You're really asking 3 different questions here:

In case you missed it, the Majors are hiring a lot of pilots. Couple that with Amazon Prime seeking 767 guys and there's your staff attrition.

Nothing, IF you are willing to study and expend the effort to learn the systems/procedures the way Omni wants you to. If you won't put in the study effort, you're cutting your own throat.

There's an interesting question. There have been Beech 1900 guys/gals who have done well and ex-heavy jet Captains who haven't. Again, the common denominator appears to be the DETERMINATION and DEDICATION of the individuals as opposed to the quality of their background.