Didn't want to jump in this debate which tilts more and more to retardation but what I can say is this - before you talk expansively about Nioh loot being exactly like Diablo you should at least play the game.
So which are the significant differences between loot in D3 and Nioh? Maybe I was sleeping when playing Nioh and didn't notice them. Sure team ninja doesn't design for 2yr olds so the system is actually populated instead of being kept to a minimum. It also takes a LOT longer to get to the item hunting part so probably most people don't get to it. But it sure looks like same system to me.
I don't even have a problem with that type of loot system but it me made mostly ignore loot in Nioh since I had the feeling it only really matters in later stages and I didn't feel like spending the time to get there after finishing the games. So what did I miss that made it meaningful in that first run?
Well, there's actually different design philosphy there.
Soulslikes are: find a weapon, learn its moveset, adapt your gamestyle to the new weapon if you like it (and it fits your build... or maybe you can change the build nowadays).
There is (usually) only 1 off each weapon with its moveset. You keep investing in the weapons you like with upgrading mats to improve their stats.
Nioh is very different. You choose a weapon and abilities you'd like to focus on and have that weapon from the start and generally stick with it (although you can switch, if you want to), improving your mastery in it, learning its new abilities troughout the game.
And you find better versions of that weapon type troughout the game. Plus you get to choose from a plethora of pet spirits, which will enchance your combat abilities and offer extra powers (which are also tailored to specific playstyles and even weapons). Plus you gather equipment "sets", which bestow various powerful bonuses, some of which fit your playstyle well.
Edit: The question concerned D3 and Nioh
Well, I'll leave this here anyway.
Perhaps the biggest difference from Diablo is how customizable everything is in Nioh. You can train Ninjutsu, Onmyo magic alongside your main arm, you can even invest in ranged combat. And you can fine tune your equipment and spirit pet to perfectly support your build.
A Barbarian won't be using magic and ranged weaponry in Diablo.