If there really was a shortage, employers would offer concessions, better working conditions, WFH, more vacation days, etc. Just look at truck drivers or hospitality for example. Just because employers say it's a shortage doesn't always make it true or it doesn't mean it's not their fault for the shortage for refusing to offer better conditions.
Depends on the field of course, but from my experience interviewing in tech, the market is very competitive now in my area in Europe for those without a lot of experience, and employers are not willing to offer any concessions besides the minimums mandated by law. Asking for full WFH is also out of the questions most of the time. This signals to me that there is no shortage, otherwise employers would be more accommodating for this.
In my country there is also a perpetual shortage of doctors and nursing staff in the public sector despite an abundance of them in the private sector. So the shortage is purely because the government is not offering the right financial incentives and working conditions for them to stay in the public sector.
My point is that "shortage" is always relative and we should look at the full story and the complete context to understand where it comes from and why it's happening, because without context I'm also having a perpetual shortage of Ferraris and Lamborghinis, though the full story is that my budget is $5000 and not a cent more, yet that information kind of changes and explains everything.
So, in conclusion, most of the times, "shortage of workers" just means people unwilling to work for the poor conditions and compensation being offered by employers, not that there's a shortage of people capable of doing said work or capable of learning to do it if offered the chance/training.