Earlier quoted context omitted.
This can't be the explanation. If it were true, the workforce participation rate would be steady. Changing jobs doesn't raise or lower that figure. A person is employed whether they scrub toilets or do brain surgery. But it's not steady. Literally millions of people have stopped working and looking for work since 2020.
Well, about 1,245,000 of them died [1], and I'm sure there were a substantial number of older working-age people who went for early retirement to reduce the chances of dying from public contact. [1]: https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm
70% of covid deaths were over the age of 70 years.