I just really love XCom. I wasn't even alive when the originals came out but after sinking hundreds of hours into Enemy Unknown/Within, going back to play the originals, and then sinking another couple hundred hours into XCom 2, my love for the series is solidified. I love how the game rewards strategic AND tactical thinking, and I love the elements of RNG. I don't believe a flanking shot should always be 100%, and the fact that it isn't creates the suspense that this kind of game needs. Prioritizing the correct targets, managing which soldiers go first, and gaming the quirky, behind the scenes stuff all comes together in satisfying ways for this series. And of course, XCom is one of the few games where even if you do everything right, you can miss all your shots and the aliens can hit all of their 10% odds shots. So if you aren't a fan of that, you shouldn't go into Xcom expecting it to appeal to you.
War of the Chosen is a much needed add on to the pretty good game of Xcom 2. While I originally found X2 better than EU/EW, My nostalgia for the non-random maps, better atmosphere, and more lovable characters of EU/EW grew stronger and I kept going back to Long War 1 instead of replaying X2. When Long War 2 came out I played that for a while, but the micromanagement and infiltration systems didn't appeal to me as much as the fatigue systems of the original. So for a while, my love for X2 took a backseat and I put another 100 hours into long war 1.
With War of the Chosen, X2 has made itself a totally unique game that sets a new standard for the Firaxis generation of xcom. The new classes are fluid and overpowered, and in response, the aliens field three totally unique aliens known as "the Chosen." The Chosen specialize in one of three areas. The Hunter uses a sniper rifle and pistol and fights in long range engagements. The Assassin turns invisible and stalks your soldiers only to materialize and stab one of them in the back, stunning them and running away. And the Warlock uses psionic abilities to create purple psi soldiers or mess with your soldiers' minds. All three of these guys are very dangerous, but also incredibly fun to fight, and eventually kill.
While the Chosen are the focus of the expansion, the three new classes warrant mention as well. You can recruit Templars (Psi Melee Warriors), Skirmishers (Freed ADVENT troopers) and Reapers (Survivalist humans) and do special missions for these factions, gaining their favor and more abilities.
Listing all of the features of WotC would be impossible, but some highlights besides the new classes and enemies are: Propaganda Photos that you can model your soldiers for, new voicelines and character interactions in the geoscape (these are underrated imo, it gives the game so much life), ADVENT speakers putting a positive spin on the mission you just completed during the loading screen, a much more involved and intense strategy layer and so much more. So much of this XPack is just cosmetic stuff and things that make the game "feel" more alive, but there's enough actual content that balances out these worldbuilding touches.
I still can't put into words what makes WotC so much more fun than X2, but it is. My one complaint remains constant throughout the entire series however: Vanilla xcom is just too easy if you know the game in and out. I can't wait to see what Long War studios does with all of the content added in WotC, cause my biggest issue is that I need more of a challenge.