Yes, the BLS graph was meant to show it has not collapsed. Nov 2016, 2017, 2018, 2019 participation rates were 62.7%, 62.7%, 62.9%, 63.2%, and Nov 2021 is 61.8%.
Also, over 20 also includes people over retirement age, so they have stopped working.
See graph labeled "age ratio". If you hover your mouse over it, you will see working age portion of population starts to decrease after 2010, and had flatlined prior to that.
https://population-pyramid.net/en/pp/united-states-of-americ...
Here is more information, but large portions of the population aging out of working years is one of the reasons mentioned:
https://www.thebalance.com/labor-force-participation-rate-fo...