Odd that the article doesn't even mention the labor participation rate ("the number of people ages 16 and over who are employed or actively seeking employment divided by the total noninstitutionalized, civilian working-age population".

https://www.investopedia.com/terms/p/participationrate.asp

A quick look at the Fred chart shows that the US is nowhere close to regaining pre-pandemic levels, and that this comes amid a multi-year decline:

https://fred.stlouisfed.org/series/CIVPART

Although the reasons may not be clear, the resignation itself has some pretty good evidence.