Astoundingly sloppy. I considered this a well-regarded series, but I'm a bit surprised that people are willing to settle for this. The writing is utilitarian genre drivel, though that's typically what you might expect for a tactical game like this. The gameplay is the real focus. Unfortunately, XCOM 2 really ♥♥♥♥♥ the bed in this regard as well.
Depending on who you ask about it, you will hear both that XCOM 2 is brutally difficult and laughably easy. The latter is probably more true given enough experience with the thing. Because the game is dependent on a random number generator (RNG) to determine the outcomes of actions, the combat is incredibly swingy. Whether an attack hits or misses has a huge impact on the rest of the encounter (and the overarching campaign by extension). Therefore, it is paramount to mitigate the RNG whenever possible, generally resulting in one specific course of action being optimal. This won't prevent extremely frustrating outcomes, but "That's XCOM, baby!" The gameplay is actually pretty fun (for a time) once you get past the initial hurdle of the game doing an incredibly poor job of communicating things to the player. There are a lot of factors to keep track of, and Firaxis' methods of tutorializing are at once egregiously tedious and yet somehow insufficient.
The real issues arise as you become more and more aware of how badly implemented most of the gameplay is. AI behavior is extremely predictable given even the blandest of circumstances. Enemies really only pay attention to whether you're in cover and whether they can hit more than one target with an AoE (area of effect) ability. As a result the game quickly becomes aggressively boring once you're familiar with each enemy type, and no amount of arbitrary difficulty can fix that.
Additionally, Firaxis puts their thumb on the scale in order to offset behavioral programming limitations. For example, when you are in concealment, the AI will gradually "patrol" over to you and simply stand there, locking down one or more of your squadmates as they wait for you to break stealth. The AI knows where you are (as if there isn't a more elegant way to balance a mechanic that the devs opted for), and this completely breaks immersion. Honestly, the whole "pod" system for enemy distribution feels horribly "gamey." I'm sure there are plenty of people that this won't bother, but when I become too aware of an artist's/creator's deliberate machinations, my suspension of disbelief falls apart.
Did I mention the game is really buggy? Like... inexcusably buggy (on top of having a generally clunky interface). I am constantly waiting for bugged animations to time out, surprised by a teammate or enemy having X-Ray vision, or loading a save because a squad member moves somewhere that I emphatically did not tell them to move.
Rather than create a holistic system for intuitive gameplay and engaging encounters based on enemy behaviors (which is an opportunity for storytelling), Firaxis is really just curating a set of narrativizable experiences that follow predictable prescribed courses. It's a toybox. Sure, novel things do happen. Sure, you can exercise some creativity to great effect, but the possibility space for both of those aspects is severely limited by the devs' utter lack of ambition. It's like all they could think to do was add more mechanical impositions (and tiresome cinematic animations). They shot for mediocre and by god they succeeded. I remember liking Enemy Unknown more, but I couldn't say how well it's aged. Not everyone is going to share my objections, and there is a good amount of fun to be had here. I just can't recommend it.
