The controls were 95% responsive for me, but I played on normal. I imagine that on hard, with more stuff going on, it'd be worse.
I'd call it Ninja Gaiden Lite, but that doesn't properly convey how stripped down everything is. All the items and upgrading? Gone. With no items, there's never any reason to explore an area to find more stuff. As you know, you only have one weapon. You change swords as you go through the game, but the second sword you get is identical to the Dragon Sword that you start with and the third sword, Blade of the Archfiend controls mostly the same, it just has different animations. There are way fewer enemies than before, most of them human. There are only 4 fiend type enemies. There is also a doppelganger boss who has more weapons and ninpo than you. If that's not trolling, I don't know what is. Everything that is left has been dumbed down. Ninpo charges as you fight enemies, but disappears, so there is no saving it until you truly need it. And if your doing well enough that you changed your ninpo, you probably don't. The UT works the same way, so instead of being a technique where you have to consider the leftover essence in the field, your position, and what weapon you use, it's basically been turned into an "autokill" button for 3-5 enemies whenever you get it. The steel on bone doesn't really do anything except slow down gameplay. It's basically a less cool, longer version of the OT's in NG2, except they sometimes also have you use X as well as Y. Lastly, I can't really explain what they changed exactly to make it feel like it does, but it's far more mashy. I think it's a combination of having longer reach, having a greater attack window, the game being slower, and more frequent staggering, but now your input simply doesn't matter as much. The only challenge the game presents is the enemy grabs, who can do so off screen and while you are in the middle of a combo, which is really annoying as they also have lengthier animations. Also, concerning the input lag, its' not exactly that it's lagging, but the game is so much slower that when you press things at the speed you would in NGB or 2, it doesn't register. For example, if you press XYX, the game will read XX instead.
There is a lot of other idiot stuff in the game, but in relation to combat, those are the main problems.