1) The storyline is almost non-existent. Most missions are about going somewhere, killing everyone, liberating a hostage, etc. The only parts that have a storyline, are mostly the ones that include the bosses. The devs obviously cared more about creating a co-op/multiplayer-friendly game, rather than creating a game with a bigger storyline.
2) From the moment you buy a helicopter with guns, it's the end of any difficulties you are experiencing with the enemies. You just fly above outposts, start spraying bullets and rockets, and then fly to the next outpost. You almost don't even need to walk anymore after acquiring a helicopter with guns.
3) The Father is the most uninteresting boss I've ever seen. Even the fight with the Father is totally meehhh. Pagan Min, from Far Cry 4, was a much more interesting boss and he was fully explaining the reasons why he was doing everything.
4) The game never gave me any reason to start activities, like hunting and fishing. Why should I do them just to gain a few more money? It would be totally different if I needed their skins to craft upgades and such.
5) I almost never needed to drive a boat, except when I had to catch a fish for a mission and when I had to collect some whiskey casks. I don't think I'm forgetting any other instance where I needed to use a boat.
6) There's no possible way to find the whiskey casks without buying a map for them. Nobody is going to swim underwater around the regions till they find them all.
7) If you are being hunted or blessed by the bosses, no matter where you are, you will magically get transported to them, even if you want to do another mission at that moment.
8) There's no actual explanation about what's happening in the ending. What happened exactly, where it happened, who did it, etc.? The ending feels bad and incomplete.
9) The specialists in the roster are incapable of defending themselves. They tend to attack head-on and never cover.
10) Most of the vehicles don't have a customization option.
11) The magnopulser gun does nothing or almost nothing against stronger enemies, like the heavies and the VIPs.
12) There's hardly any reason to waste your in-game money. No need to buy guns, vehicles (except the helicopter with guns, of course), etc. I only liked customizing my guns with the few (sadly) upgrades that they had available.
Sooooo, why should anyone like this game? Maybe it's fun if you play it with friends, but that's all. But keep in mind that it won't save your progress if you're not the host of the game. The only good thing is that I didn't experience any bugs. It's not worth its current price, but maybe if you ever find it for around 15-20 euros, you can buy it if you really want it.