The Boss is a *somewhat* interesting character, you see what they were trying to do with her, you see that she's actually a good guy all along but she has absolutely zero margin for error. The problem as everyone else said, is that she and her relationship with Snake is not fleshed out. At least not until the cutscene before her boss fight, where she infodumps most of her life story. I like how she empties her whole heart once in her life while trusting that the man in front of her won't just shoot her. And Snake does a Keifer Sutherland and just watch and listen for the entire time. I dunno, there's a level of respect and civility between two characters that I can appreciate. Another cutscene where she's fleshed out is the "big reveal" narrated by Eva. I also like it, but it's still a big problem actually. There's only two moments where we can fucking care about her and they're at the very end. Maybe that's why people praise the story a lot, because that's the last thing you see in the game, it's a big finale that makes you forget about the mediocre writing of the Boss for the first 95% of the game.
Also her tombstone hides her birthdate and her character bios during radio calls hide everything about her. I know she's a top black ops agent and maybe we can pretend she's given up her life to serve her country and all her files have been erased.... but Major Zero, Sigint, Paramedic, Eva are also involved in super top secret black ops shit and all their info is revealed so that's not an excuse. I hate when they make a character so mysterious and illusive that it ultimately makes me not care about them at all (wink wink Ada Wong wink wink).
Opeworld, sandbox games are overrated. I want a tight, on rails experience for most games. Open world is just an excuse to have poor writing
Look how cool it is, you can do this game in any order you want! This is FREEDOM! Gamer freedom is the best thing ever! But wait, if you do something in a particular order, we have to take it into account and create multiple different cutscenes because one thing might have happened or a character might be absent.... ehh they won't notice. Let's make a disjointed irrelevant story and call it a character driven story driven game.
Only game I've seen this done right (at least that I can remember) is Ghost Recon Wildlands, because the story is basically "take down this entire organization by picking it apart one by one", so it really doesn't matter in what order you do what, as long as you take it down. You get convos/cutscenes related to a particular lieutenant when doing their quest line, and when you take down a major boss, you get some kind of general update, like after taking 2, the leader calls your team and tries to bribe you into leaving the country.