Although quite captivating to play, you are stuck at every turn making a decision. Do I fight this enemy or run by them? Do I take this item or leave it behind? Do I attach this parasite? What do I spend my material on, knowing none of it is permanent anyway.
And then you get to the bosses. You have to run around to maximize yourself before you should even think about attempting to fight the boss, but every time you explore something new, it gets more difficult. So, in other words, you stay at the same level of being underpowered the entire game.
While providing endless amount of game play, you essentially are just running round in constantly changing circles trying to find a better weapon or more power, while if you die, you keep nothing but your ether, your sword (WHEN YOU GET IT) and your alt-fire.