Sekiro is a fantastic game with great level design, but I see a lot of people saying Nioh is better. But Nioh isn't better. Nioh sucks, and here's why:
The biggest problem by far is the enemy variety. Once you've played three levels you've played pretty much all of them. Also, some enemies are terribly designed- consider Amrita Fiends. They have a ton of health and if they hit you they will probably kill you, so they are extremely slow and take swipes at you once every ten seconds to compensate. The end result is an enemy where you walk up, attack twice, and walk back, repeating until death. There is practically no chance of dying if you do this. The only reasonable possibility they have of killing you is if you get impatient and wail on them too long or get overzealous after a stagger. You will probably spend at least three hours fighting these guys if you finish the game. This is not actually hard, it's only superficially difficult and winds up being a patience test.
Boss design is unpolished. Some bosses have unreactable moves that deal tons of damage, and other bosses have attacks that are nearly unavoidable at certain ranges. Souls games do a good job of regulating difficulty so that players only struggle with well designed bosses, but Nioh absolutely does not- for example, Umi Bouzu is fairly difficult and he's abysmal.
There’s less weapon variety than there initially appears to be- 1kat, 2kat, and spear have loads of moveset/ability similarities with a few gimmicks or stances to meaningfully separate them. Kusarigama and Axes are substantially different from other weapons, but the end result is about three substantially distinct weapon classes. There are a lot of weird buffs, but offensive spell variety is sorely lacking.
Nioh is a struggle to stretch three respecs into enough fun to slog through a horribly repetitive game. It's shit, a 5/10 that got rated 9/10 on metacritic because game journalists only play video games for two hours.
