Circa 1988, the Alberta government had a plan to put a lot of marginally unemployed people to work. It was training them to repair personal computers. They were called 286"s and 386's back then. The government filled the student seats of the computer repair program at a technical college for four semesters. Very few graduated. It was hard to get these students motivated and most of them probably did not have prerequistites to do well in this program.

The lesson: we should not depend on screwups to get work done! This is why any jobs program, where they are forced to attend work, is not likely to produce lasting results. And it is costly to monitor these screwups.

The civil projects started by FDR did put many workers to work. But if they were screwups, they didn't last too long on the construction sites.

In this Medium article, I talk about how it is better and cheaper to give screwups a UBI than to find work for them:

https://medium.com/common-sense-please/keeping-screw-ups-out-of-the-work-force-39afd99ea26

Unless there are some mechanisms to address the psychology behind the screwups, then there really is no mechanism for a "full employment" program.