I'd say most of us agree Nioh is an excellent game. General consensus seems to be that it's strongest features are complex/fun combat, a deep loot system, and challenging but rewarding bosses. On the other hand, the main argument against the game on almost every post/review has something to do with lack of enemy variety.
Of course, we all know the comparisons to Dark Souls/Bloodborne on this and many other aspects of this great game. However, one thing I haven't seen mentioned in regards to enemy variety is the fundamental difference between Nioh & Soulsborne enemies. In Dark Souls, if you encounter a skeleton in the first area, it will be that same skeleton you could encounter in the 4th, 5th, 10th area. The enemies in Dark Souls are static, meaning their stats don't change based on your progression (until NG+). A hollow with a torch is always going to be a hollow with a torch, and his moveset/attack/health won't change throughout the game. Or a massive stone gargoyle might be a very difficult enemy early on, only to find later in the game you're dispatching several at once. The reward aspect in terms of RPG gameplay and leveling up your character, is that you get to take out progressively bigger/badder mobs of enemies, learning new skills and weapon types. This system also creates a sense of a cohesive habitat or environment, in which these enemies feel native to their living space, and you are a level 125 Paladin coming to ruin their day.
In Nioh, this is not the case. The enemies in Nioh scale with each mission level, and you're fighting the same character model Yokai in mission 1 versus mission 10, but their stats have changed. Later in the game, the Yokai become slightly more scary looking, when they develop a bad case of crystalitis growing off their heads. However, for the most part we have one enemy (Yokai w/ a sword) and this enemy will be low level, medium level, or high level based on your game progression. There is no lore explanation behind why these enemies get tougher throughout the game as you progress, which could have been a viable approach. You will almost always be fighting one at a time, and because it scales with the mission level, your experience will be largely the same every time. There will be no feeling of "man, I'm so strong now – that enemy used to be so difficult but now my +10 spear destroys him". Granted, as you learn each enemy type you naturally get used to their moveset and will be more effective against them. However, there is much less feeling of conquering this world through character development, due to this difference in enemy scaling.
I think most negative sentiment regarding enemy variety is solely focused on lack of different character models to defeat. However, I think it's a deeper issue and has a lot to do with how these enemies "feel" within the world of Nioh, and how their scaling is the primary feature which lends itself towards them feeling stagnant. Just wanted to point this out, since I haven't seen it discussed here. Nevertheless, I'm enjoying the game tremendously and hope you all are too.