I'll add that there are some feedback loops making it worse. When these organizations aren't available kids are more dependent on their parents for something to do, which makes the already strained parents even less likely to take on volunteer work.
And then kids who grew up without mentors are less likely to try to be that for someone else.
Basically the orgs don't have enough volunteers to do important things, and the people don't volunteer because the org isn't important to them.
Yes, the network effect and cumulative impact is profound.
If I were to make a lightly educated guess - those who were teens in the 40s and 50s saw the world of their parents and their sacrifices, along with the totalitarianism of the USSR and Nazi Germany, and decided to pursue individualism over community. So as they got to an age to participate they opted out, as well as increasing the total social individualism. And here we are.
I don't know exactly what the way out here looks like, but I believe it absolutely means involvement with local organizations. Kiwanis, elks, rotary, religious, etc.
And then kids who grew up without mentors are less likely to try to be that for someone else.
Basically the orgs don't have enough volunteers to do important things, and the people don't volunteer because the org isn't important to them.