The thing is when you look at the history how (semi) open world games originated it has a couple of reasons but a very notable one is the hidden wall..

It's something you never hear anymore but a major complaint of many gamers was the hidden wall. A 2 feet fence you can't jump over, or just literally a hidden wall that you can't move anymore in that direction because the game doesn't allow you.

That breaks immersion and (semi) open world gameplay is a good way to counter that. With semi I'm talking about games like halo, big maps, but (hidden) walls of the maps are intertwined with the envirmonment, like cliffs or mountains.

Open world gameplay also became more popular because you could offer more content but a lot of developpers cheaped out in this regard by making missions dull with rehashed content and ubisoft is probably the worst in this (you mentioned captured this outpost and the first thing I had to think about was ubi's far cry series).

Maybe you should try the real successor of the first far cry, which is not far cry 2 but crysis. Allthough far cry 2 is one of the best far cry's imo, but that has a lot to do with the fact that ubisoft had to compete with crytek, who made the original far cry and also crysis.