I find the solo side of it compelling; the whole process of scoping out a base/town etc, tagging enemies, assessing the best was to tackle it, and then executing that plan, to be really engaging. I've almost 100%'d 3 provinces now, and am still enjoying it. There's enough variety in the environment, and where the towns/bases/etc are placed to keep it interesting, for me anyway.
Things like jammers that stop you using the drone also force you to think differently about a given scenario.
A lot of reviews that are coming out at the moment seem to focus on the "hu-ah" bro-ness of the protagonist and his squad buddies and how Bolivia is huge and beautiful, but it's all viewed down the barren of a gun; well duh, it's a bunch of military commando types doing covert ops in a South American shithole - it's all about guns and shooting dudes in the head with said guns!
They seem overly harsh to me, people getting all bent out of shape about the politics rather than taking the game for what it is (as opposed to taking the game as a glossy postcard provided by Bolivia's Ministry of Tourism).