I've played FC4 and 5 and this one is bigger and more complex. It can be a little overwhelming at first and tbh I wasn't that jazzed about it when I started playing.
If you don't dig the Latin American rebel vibe or language then you're going to have a bad time because it's immersive and pervasive (the same way RDR2 is all about being a bean-eating cowboy and that was not my thing). But I'm into this motif overall so willing to keep playing. But I'm not riding any horses.
It probably turned around for me when I fully grasped the modification/resource system, and the guerilla network infrastructure. Grabbing a few choppers helps, but only after you take out some anti-aircraft batteries.
There are flaws in the UX when it comes to comparing weapons and mods, and the resource system is overly complicated so the initial impression there is negative. There are separate camp resources and weapon resources and it's not clear which is which until you play a while. Games no longer come with manuals and even tutorials have been scaled back so you're expected to look shit up online, and that's what I had to do for some of the more rare resources. You can't just look at some scrap you're collecting and know exactly what it's going to be used for.
That said, gunpowder is the #1 critical component for weapon mods and it's found in FND chests and supply drops. Start looking for those and you can start leveling your weapons. Up to a point. Then you have to figure out how to get the more advanced components, which are only even usable on the more advanced weapons (which have more mod slots).
If I could do one thing over at the start (other than not spend money for any weapon other than a rocket launcher since they can be found all over the place in chests) I would collect as much metal and gasoline as possible and visit each of the 3 area ally bosses and immediately set up the 2 unique camp outposts you're allowed per main site. This is another unclear element until you dig into it, and realize you have to have a hunting lodge to find the alpha animals which are then traded for rare components needed for higher level weapon upgrades. I spent too much time in one camp to start, thinking the other areas were deeper into the game than they were, similar to FC5.
You also have to embrace the full guerilla network objective, as this is not the kind of lone wolf experience where you just traipse around the wilderness shooting hawks and taking over bases. The missions stack up and they overlap within the guerilla network storyline.
Added to that are special ops missions and commando raid mini games that have additional rewards. These feel like they were either tacked on or are remnants from an earlier attempt to develop the weapons progression. Then there are other side stories and treasure hunts and whatnot. Another unclear element is how to obtain leaders (Yaran Stories with people as rewards) needed for the mini game ops.
Combined with the anti-aircraft objectives which yield depleted uranium for "supremo" weapons (rechargeable special mods) the system becomes ridiculously overdone (pesos, depleted uranium, special ops black market moneda, resources, experience points, etc all used as various forms of currency for various things). It's ambitious but probably too much to keep track of by about double.
Some of the same FC glitches are there, such as hanging load screens and choppy frame rate or sound dropping out after the game has been running too long, all of which are usually fixed with a restart. The latest game update on Tuesday marked all my weapons and gear as new for some reason and the icon doesn't disappear when selected. Minor annoying shit like that crops up.
But overall once you understand how they've set it up, and can move more freely about the landscape, you see how vast and cool the entire world is and how many options you have to explore and f*** with it.
This could take a while.