I played XCOM 2 when it first came out, but went back to it a few weeks ago. This is such a solid, well-designed and well-balanced game. I just finished my second run through the vanilla game, and I'll probably start War of the Chosen tonight or tomorrow -- never tried that one before, so while it's not new, it's new to me.
One thing I had forgotten is just how high-variance this game is. I actually failed the final mission on "hard" (whatever it's called -- difficulty level 3 out of 4) on my first try last night. Basically you have to kill three mini-bosses in a row while dealing with mobs of various enemies that are being thrown at you at the same time. I killed the first two no problem, but then get myself into a position where I had no means of damaging the remaining boss -- he teleported into a spot on the map that I couldn't reach -- and there were way too many enemies left for me to survive them getting a turn. It was hopeless.
But fortunately I have no moral objection to save scumming. I reloaded a save, and literally changed one move. Instead of attacking that last boss with Soldier A, I hit him with Soldier B instead. For some reason, this time the RNG gods teleported him right by the rest of my squad, and I was able to finish him off with no drama with a bunch of moves to spare. One single move coupled with a favorable roll (or, more accurately, a not-ludicrously-unlucky roll) swung the outcome from game-ending-squad-wipe to easy victory.
I have no idea how people do Ironman on the higher difficulty levels. There's just no margin for error and often no margin for misfortune.