I know people who go to yeshivot hesder (I know one at the moment who is actually a chayal boded who is in a yeshiva regiment) and then are all together in the army and from what I’ve heard it can be a fantastic experience. (I was watching the hashvaah for this soldier’s regiment, specifically the part where they all swear allegiance to the army and the state, and you can hear regiment after regiment say “ani nishba!” and then, all of a sudden, one that says “ani matzhir!”- the yeshiva regiment. They’re very accomodated and are doing something that is important to them.
A pretty major point in general in this discussion is that people are going to have varying opinions about the viability of the army for frum kids because people have different opinions about the things that frum kids need to make the army spiritually good enough. Someone who needs a black suit and hat and 24/7 learning will obviously not have that and perhaps descend as a result, as they are used to nothing different; someone who grew up expecting to go to the army and expecting to make things work will have more of an ability to do that.