but, and correct me if I'm wrong, the actual fighting is still mostly done by guys with rifles.
While this is technically true there is much more to be said about combat than "fighting with rifles". The complexity of combat operations is incredible... The individual specialisations out there in modern armies are getting more and more complex in increasingly demanding environments... You cannot simply assume you give someone a rifle, some ammo and a little but of training and expect them to perform in modern combat.... it just doesnt work that way anymore.... This shows in the way basic soldiers get trained now... BCT in thw '70 was done within half a year... usually a 3 to four momths. After that they were immediately pressed into service for half a year.
The comabt trainings are still jhust as long but the current standard is to such an extent now that as soon as you come straight out of training, you basically know how to hold and shoot your rifle. At least another year of training is required until one is a fully functional member of the unit and able to be an individual and independantly operating soldier. Not to mention they have no actual specialisation when they come out of basic, that still needs to be trained.
Then there's the matter of officers. If you have a conscription army, you need conscripted officers. The minimum amount of training you undergo as an officer in the Netherlands is 1.5 years... and that is for combat service support unit. Go to manoeuvre and you're stuck to at least 2 years.... and that is for people who already have a bachelor. These days you need officers with a high intellectual capacity... The americans thought they didnt and are currently facing the problems with subaltern officer.... well.... basically being too stupid.
There is a reason the US cannot seem to fucking properly conduct stab ops.... a significant part of it is because its personnel is too stupid... combat isn't any less complicated... especially if you're fighting a numerically superior foe, you need to be the quicker, more smarter army... you cannot just beat a numerically superior foe by somewhat increasing your numbers.....