I've been a 42B for a while now, here are my thoughts:
This is honestly a dead end branch for officers. As an AG officer, you're essentially the bureaucrat branch of the Army. You're the paper pushers who do have an important job, but not necessarily a specialized one. As an AG officer, your by the reg job is to advise the commander on all things admin and HR. Your daily job will mostly be serving as the punching bag for the command team for why shit isn't working, being the POC for the admin jobs no one else wants to do, and generally getting shit on for processes that are largely out of your control. You will always be just a middle man for paperwork going up and down the chain, which makes you look like an overly paid bureaucrat.
Now, it's the Army, and paperwork is how ANYTHING gets done. But that's beside the point. As an AG officer, you'll never be credited for doing vital work in the background that keeps the command from getting relieved, you'll never be credited for having accurate strength numbers, or making sure everyone gets their participation awards at the end of tour, or making sure the commander's board file is good to go so he can go abuse an S-1 at a higher level.
To be clear, most AG officers know this when they sign up, and they're ok with it. It's not a glamorous job, but some people enjoy it. So what's the problem? Anyone can do it. Seriously. As an AG officer you don't learn a specialized skill set, you learn how to dig through regulations, and that's basically it. Everything you do is basically conforming to a currently existing process, and as long as you don't fuck it up, you'll be fine. There's a reason AGBOLC is the shortest one, there's a reason you don't see AG officers in command, and there's a reason you commonly see non AG officers stuck in S-1 roles as filler. Because it's a generalized field with no unique skills. It definitely isn't "Human Resources." You will learn nothing that is relevant to a civilian HR job.
I truly believe we could replace the AG corps with civilians and not lose anything. The AG corps has generalized itself out of usefulness.