The fighting, the pacing, the level design and especially the loot system in Nioh and Nioh2 have nothing to do with dark souls,. It's difficult, 3rd person and has level checkpoints, and that's where the similarities end.
If that counts as a dark souls ripoff then there have been hundreds of ripoffs before dark souls even existed......
Mimics weren't invented by from software btw, these are from the D&D universe originally.
I'll give you the loot system. Yes, the combat is different with more weapon types and the living weapon, but still similar with blocking, dodging, and attacking. And there of course is the stamina gauge which is similar. There is the similarity with saving and enemies respawning and when you die you leave your souls (or whatever it's called in Nioh) behind. And if you die before collecting them, you lose them. EXACTLY THE SAME as Dark Souls. So no, that's not "where the similarities end."
It also has the similarity with the co-op system where you can't just easily play co-op. You need a useable item to summon someone. It's the same type of archaic system.
Come off it, of course Nioh is HEAVILY inspired by Dark Souls. If you don't like the term rip off, that's fine. To me, it is. I might not be the biggest Dark Souls fan, but I've played all three games and Nioh feels like a rip off to me. It's its own thing, sure, but there are far too many similarities to write it off as unique.