Shadow of War is both fun and tough, particularly at the highest difficulty setting (which I highly recommend). Unlike the original Shadow of Mordor, you can't just roll through dozens of Orcs with a blazing sword, taking heads and limbs willy-nilly. Sure, you can try, but you'll soon find the ranks of Orc captains overflowing with grunts promoted for cutting you down. And they won't let you forget it. And there is a much stronger focus on the captains in this game over the original, much less focus on fighting the Orc grunts wandering around - and unfortunately less benefit, since you don't get experience for killing the lowly grunts. So, if fighting hoards of Orcs was the thing you found the most fun in the original, you do get less of that here.
Skill progress is slow, and this really adds to the fun and challenge - as you (quite) slowly level up, the captains get slightly easier, and your odds of surviving masses of Orcs slightly improves, and this slow improvement allows you to appreciate each success. But as you level up, so do the captains, so there is a good balance. It takes a relatively long time to expect to win nearly every fight you walk into.
The extra challenge you'll find in Shadow of War really makes this a game worth playing. Every Orc captain you take out will give you satisfaction beyond what you could hope for from Shadow of Mordor. Each time you come up on a captain early on, you are already half expecting that, rather than win, you are most likely going to just do some damage and run away, if you survive at all. And herein lies the beauty of the new and improved Nemesis System. These Orcs not only remember your encounters, and not only bear the scars you give them, but they'll actively hunt you down, ambush you, or hang out with other captains, waiting for you to attack.
In fact, the variety of ways that you can hunt down, stumble on, or get suddenly ambushed by Orc captains far outstrips the original game. There's a life to it that the first one can't match. Sure it's all scripted and run by complex and convoluted computer algorithms, but it comes together so well and naturally that it doesn't feel scripted at all. And as you kill and get killed by the Orcs, the web of alliances and vengeance gets more complex and interesting. Cleave an Orc captain clean in half and you might find his buddy hunting you down for revenge, only to find later that the cleaved Orc has since been sewn back together (quite literally), and is out to get you.
It's just a fun game, there really isn't any way else to put it. A great mix of fun and challenge.
If you are avoiding this game because you've heard about the "loot box" controversy, don't worry yourself about it. I was 9 hours in before I even noticed where to buy a loot box, and still have no interest or need in buying one of these "gold" loot boxes, particularly with the new online fight pits and online siege - just get your gold that way. In fact, loot boxes are such a non-factor that if it hadn't been mentioned to death on forums and reviews galore, I probably never would have even noticed it at all. These special gold loot boxes can probably get you ahead in one way or another, but I have so much fun running around the map hacking off Orc limbs only to see them sewn back together later when the Captain I assumed was dead tackles me off a rooftop in a surprise ambush that I build up enough in-game currency and experience on my own. That being said, I got all the way to Shadow Wars level 8 before losing a siege, and have never paid real money for a loot box. They don't get you through the game faster. You don't need them. So relax, and try the game.
The only real negative with this game is the same thing with almost any game - the repetition factor. Each land holds a citadel or castle that you will have to eventually siege. The process for preparing for the siege, and the siege itself, is essentially the same. The major differences are the race of Orcs in the land, the type of citadel, the number of warchiefs, etc. But the process is the same. The personalities and nemesis interactions help to relieve the potential tedium, but it's not perfect. That's why I give this 4.5 stars instead of five. You are basically repeating the same action over and over as you siege castles. Fortunately the personalities of the captains and warchiefs, the great variety of Orc races, and the plot related quests help to balance it out. Also, you have a variety of options when it comes to tackling new lands - use branding and infiltration to weaken the castle, or kill off the warchiefs without placing spies, or just immediately siege the castle with no subterfuge at all. Each land carries enough variety and offers enough options to prevent outright tedium.
The Shadow Wars could also be considered tedious, but if you've made it that far and like the gameplay, it isn't a big deal. If you find the game and game play fun, it simply won't be a grind. If you don't like the game play, then it is a moot point.
It is definitely worth picking up, and if it ever goes on sale, it would be a requirement to pick it up. It really shouldn't be missed.