Really the pandemic was an accelerant. But even without it we also have a relatively stagnant population (declining birth rates; growth rates of the US population declining between 2010-2020 from a combination of lower birth rates and a decline in immigration). All while also getting to the point of whole bunch of boomers retiring as well.
IOW, even without the gap in employment created by the pandemic, a shortage of workers was likely always an inebitability just due to simple demographics. Too many boomers will retire, not enough of younger generations to replace.
Kinda hit on this as well in the discussion about the railroad workers a while back; that's an industry that is facing a pretty steep demographic decline on the horizon, and while the Class I's may see short term gain from not revisiting their time off policies, long term, to discerning prospective Gen-Z workers (not to mention the generations that follow) in an environment where they are given more options, messaging that kind of hostility to even a modicum of sick leave seems counterproductive in attracting future employees to choose a career in that field.