The bottom line is that the vast majority of these potential recruits “just need some work”, before they enlist.
The easiest solution to this is to set up pre-enlistment camps where they get individual diets, lots of exercise, tattoo remove if possible, and classroom to make sure they are literate, and while they are at it, to give them a big dose of military history and culture.
There would be three tracks to this program. A one month camp for those who are marginal, to get them up to standards. A three month camp for those who need a lot of work. And a six month camp for those with critical specialties, but who are otherwise in sorry shape.
Optimally, the camps would not be run by active duty personnel, except a few TRADOC (United States Army Training and Doctrine Command) evaluators, but by veterans. It would have some support staff for medical evaluation, maintenance and logistics.
Hell, we had Fat Boys Squadrons when I joined in 1969. Also, Skinny Guys Diet regimens (I was in one until they figured out I was stronger and more agile than anybody else in my BT class.) I still hate macaroni, spaghetti and potatoes. I think they’d do better to have pre-enlistment motivation platoons.