When you have a comoany that knows how to do a certain thing , aka one of those evil corporations, getting hired by the federal government, some people want to do a lot of paperwork and stuff to keep track of what's going on, and other people go crazy with it.
If we're doing something important, like killing Hitler, or trying to beat the Commies to the moon, federal procurement can be remarkably efficient. Clear goals, and the stated willingness to accept some waste as long as the job's done, can do that.
Unfortunately since about the mid-1970s (Watergate you say?!), approximately zero "waste," of any kind is tolerated on any federal project, as this is "profiteering" or "wasting the people's money," so a lot of contractor time is spent on compliance. This makes the process incredibly loss-averse, and probably too risk-averse to actually accomplish anything.
The reality is that Elon Musk is able to do a good job, because he can destroy two or three recovery barges in a row and he doesn't have to explain it to anybody but his accountant. If the SLS had only one slip-up like that there would be a bloodbath of firings, senate hearings, press conferences with the President, and maybe the entire program might be scrubbed. Back in the late 50s NASA screwed up these kinds of operations all the time, but the American people tolerated it because of the Cold War. Nowadays the budget is so tight and public accountability is so fierce that frigging welding assembly subcontractors are apparently front-page news. We probably built and destroyed five facilities on the scale of this thing during Apollo and nobody batted an eye at the expense.