Except for the secret areas under the elevators, what is there to explore? You have many branching paths, but each path on its own is just a linear corridor with nothing to do except walking (where, at best, you have to face a very bland and simple platforming or combat challenge). You have four items that unlock new forms of movement or new areas/secrets, but usually these areas/secrets are just a single screen with an item in it. You get the "blood platforms" item very early in the game, and you have no reason at all to ever take it off, so that barely counts. The "growing roots" item could be cool in theory, but 90% of the times the root is just there to let you gain a single item and nothing else. The "poison" item can be used like two times, and, again, it only lets you take an item, it doesn't really unlock new gameplay challenges. The "abyss" item is the only cool example and I have no real complaints, but it's just ONE single redeeming aspect of the exploration in this game.
Combat is almost never engaging or challenging. You have three kinds of enemies: (1) require you to just spam attacks until they die, (2) require you to wait for their attack and block or evade and then spam your attack until they die, and (3) require you to attack, evade, and repeat. There's no challenge involved, and you almost never have to adapt your playstyle to the enemies/environment. Simply spamming the attack button gets you through more than half of the game. The optional arenas could be fun, but combat is so easy in this game that they are always over in a matter of seconds. Some bosses have fun mechanics, but most of the time the combat routine doesn't really change from what you have already experienced against regular enemies, because you can spam attacks and, if you remember to heal when your health is low, they can't really kill you before you kill them (there are a couple of notable exceptions to this, but that's what they are: exceptions in an otherwise boring combat system).
On the other hand, the art, atmosphere, and narration are 10/10 and completely redeem the entire game.