MILSIM isn't really a binary concept, it's more of a spectrum. The deeper you go into the simulation side of things the further you get away from military, and vice versa. Sure you could have a 30 hour game where two sections are to patrol a forest, interact with locals, investigate and try and find the insurgents operating in the area (With, maybe, *gasp* one life only?) Heavily focused on a scenario which you could very well encounter in real life with rules set to reinforce that scenario. Most people don't really consider the "talking with the locals" aspect military, instead the image always comes back to two nations duking it out. Cool. No problem with that. As you structure the rules to really focus on that element of it and streamline the event, you lose out on the smaller nuances and end up with games where all you do is capture control points and react to enemy movement.
There are very few games that I have felt combined some of the best aspects of both; the shooting and the little bit of roleplay to manipulate the play space. Most of those games have been under Brians command. What makes those games really pop is that the instructions are very clear on what the scope of the game is; what is and is not possible. At last years Deadfall he stipulated that there civilians in play, how to detain them, how to search them, and what each teams instructions were on encountering them.
At last years Deadfall there was a point where I was with two team mates and our path was directly blocked by about 20 JOTF members. I gave my weapon to a team mate and offered myself as a distraction. I went up to the soldiers, started talking to them, making a bunch of noise so my friends could sneak through the forest without being heard. I was searched, detained, and brought back to their HQ and questioned. I was eventually executed when they found out I was an insurgent... Before putting a bullet in my head they were being nice, offered me food... Their security was lax and I overheard some things, and had four distinct opportunities to grab an unsecured weapon, shoot my captors, and escape. Everything was in play, within the scope of the rules, and wouldn't have been a surprise to players had I chose to make a Rambo attempt. My team mates made it past their patrol back to base, I collected intel; all without a single round being fired (except for the one that went into the back of my head)
Thats my personal favourite blend of MILSIM. It allows you to think of solutions that may or may not involve dispensing BB's at foes. When you have too much roleplay people won't sign up, and if you have too much GOGOGOGOGOGOGO MILITARY then people consider it a skirmish. Whether a game is 8 hours or 24 hours doesn't really change if it's a MILSIM. I think what we can agree on is a majority of events billed as "MILSIM" in Canada, isn't.