The shortage is of experienced airline pilots capable of sliding into the LHS of an airliner.
Up till now there has been ample numbers of experienced FO's around the world who are able to do this. Now there are not so many.
What airline managements are yet to fully comprehend is that these pilots have taken an absolute minimum of 10 years to get to that point from ab initio. MPL will probably fix the problem.... in 10 years time. Until then, any airline that wishes to expand is going to have to bite the bullet and increase its T & C's in order to lure the experienced pilots it needs right now away from whatever position they currently hold. The laws of supply and demand guarantee that this will happen.
In Australia, Qantas is the only airline with large stocks of experienced first and second officers available. That is good for Qantas, but they had better start to value them now before they lose them to other airlines desperate to keep their fleets flying.