> Apollo program doesn’t seem to be a good example of a space pipeline that is sustainable for a few decades at least

Correct. OP suggested the root of the problem is we haven't made "these workers government employees." The Apollo programme had lots of government employees. Commercial interests clearly aren't at the root of the problem.

Im pretty sure the government employees working on Apollo were mostly already there before the program or stayed there afterwards, so their tenure was probably much longer than 3.6 years. And a lot of work on Apollo was done by contractors (for example building basically all flight hardware as far as I know).