The only other thing you could learn in regards to tactics in my opinion, is how to take on certain situations. I mean, with the diversity of mission areas and objectives, there is always some kind of lesson to be learned. You are fighting against competent and sometimes highly lethal enemies that will bend you over and beat you a** like no tomorrow if you screw up, which makes the lessons learned that much more memorable, because you died twenty times before you actually got past it XD
But truthfully, you learn how to rely on what you have, cause lets face it, there isn't constant resupply when you need it in the original Ghost Recon, which killed me more times than I care to remember. As well, you learn how to command a small platoon size force over an immense landscape with multiple routes to be taken to get you to the objective, which can often break apart a small unit because of the paths taken and the chances of being ambushed along that path.