Never had this impression myself. Sekiro enemies felt much more varied than Souls, from the bandits looking like bandits while sacking that starting village, to guards and soldiers and those snake snipers feeling like normal combatants. Only the monks in that mountain monastery felt ghoulish, but even then some of their guards felt pretty much alive (and those big hat ones felt like they were on CRACK).
Dunno man.
This is one of the most basic bitch you meet in the beginning of Sekiro :
It's not an outright zombie but.. does the skin tone look human to you? I mean it and not in a racist way. This is not a healthy asian skintone, or arab, or black, or anything human. All the regular mooks look like there's something wrong with them.
Then you meet something like this mini-boss :
That thing looks sickly and more like a zombie than a proper "monster" or yokai. I mean, some yokai of asian myth do look diseased but this just looks like a giant traditional zombie to me. Look at Nioh for a more japanese vision of monster folklore.
This is Genichiro, your main foe throughout the game. Interestingly, the same skin tone as the ogre (at least on my monitor). Dude looks like he's half dead.
Then the deeper you go in the game, the more fucked up people look.
It's hard not to feel like you're going through a post-apocalyptic world where everyone got fcked up just like in a souls game.
Really, the only characters that look normal in the entirety of the game are Owl (well, normal as in healthy, because he's strangely gigantic for a "human".. is he really human? ah, whatever, it's a From game), the kid and Emma. Of course, any From game needs a good looking woman even when the rest of the world looks like it came from Satan's butthole (not to mention, your own player character that looks like a disgenic abomination because of the character creator system in games other than Sekiro).
The noble garments actually say everybody is losing their minds and living "immortal, pointless lives".
Interesting, but which garment? I tried looking it up but couldn't find it.