There is a lot of fat to be trimmed from the DOD, and a lot of it is wrapped up in bureaucracies and, for lack of a better term, graft.
I listened to a podcast about the B-1 Stealth Bomber. The DOD managed to go from urgent need to a successful prototype in about 9 or 10 months back in the 1970s. We'll never see that happen again in the US. The problem is that the contractors have been smart about spreading the jobs across multiple states and sub-contractors. So, when anyone starts talking about cancelling a program that isn't needed, is too expensive, or isn't ready for prime time, the word goes out to to the various local and federal politicians that 500 jobs will go away in this state, and 200 hundred in another, and 1,000 in a third. And all of a sudden that program becomes critical again or gets put on "additional research" funding. This isn't a partisan thing, both Republicans and Democrats cave in with equal ease.
If we want a leaner, more efficient DOD, then there needs to be an acceptance that it will put people out of jobs. Perhaps a lot of people. And that's easy to talk about, but harder if you're the avionics wiring specialist with a job at Northrup Grumman on a program that's on the chopping block.