There's a whole raft of reasons why we have a pilot shortage I reckon. From the Airline bean counters who want more profit at any cost to no foresight by same. There's only one thing in the operating cost structure of an Airline that is directly available to that Airline to be controlled & that's the HUMAN element of it all. Minimum staff means more profits but that short term 'fix' has long term consequences that we are now seeing these days. The only other hole in the leaking ship of Aviation is that the job is no longer considered glamorous or well paid, IT & other industries are in vouge these days, flying a jet is just a job & not a considered life time career de expense just getting theret!
The answer? Well there is none for the foreseeable future, the world will be playing catch up for a very long time!