I agree, it doesn't make sense to have all those half trained kiddies released back into the community and one class does not an army make. I'm all for the STC and remidial classes.
I'm not sure I'd have every jounin take on a kid. A lot of them don't have the personality for it frankly. Especially if we include the specials and go by the system you get to be a jounin if you're all around good and have some leadership abilities, special jounin if you're freaking strong or talented in one particular area but are somewhat lacking in the desired personality traits
. Besides you get to the highest level, you don't want to babysit and you don't want dead kiddies if you piss off a death machine with a hair trigger.
Maybe make apprenticeships or mentoring more common but I wouldn't have it compulsory.
Also maybe have extra classes kind of like what Kurenai was doing in team 8. Kids who display a talent in whatever (genjutsu for example) or want to focus on it have extra lessons from a specialist as well as working with their usual sensei. This way kids in the STC and remidial programs who display a talent in one particular area can get some higher level training too. It means talent isn't wasted because their sensei doesn't share it.
For example with our (old) Team 4 Ushio would have extra lessons with genjutsu and seals, Kontan with tactics and ninjutsu and Hotaru with hyuuga techniques and some medical stuff rather than their sensei trying to teach it all.
(Food for Though and People Lie both have pretty good world builidings. PL has that whole chapter about the world and military etc)