For the fast-paced combat that the game intends, controls are too clunky and you get caught in every piece of the environment. Shooting is impractical since aiming is tied to the movement stick.
The game itself is too easy in terms of gameplay, proving too much healing. It is only made hard by the clunkyness of the gameplay.

The worst of all is the meaninglessness of co-op. The player 2 (P2) can't interact with anything, pick up items, or heal. This forces P2 to have to jump off the map any time you want to heal. Also, P2 is forcibly teleported to P1 any time he hits the edge of the screen. Since the camera moves based on P1 position, P2 will unintentionally teleport in middle of chaotic fights. This is specially annoying in boss fights.

The devs really didn't want to hire translators so they said "♥♥♥♥ it, remove all dialogue". They didn't want to do music so why not just press a bunch of notes and layer that for everything (seriously I had to turn off music like 5 minutes into the game it's putrid). And they certainly could not be bothered to add animations for the player character interacting with stuff so just add a little drone that does it via telekinesis or something

The environment is cluttered so you get stuck in a rock every 5 picoseconds. There are some cool setpieces and that's about it. I don't see much reason to comb through every nook and cranny when the only reward you can offer me is 1/4 of an upgrade token which is useless on it's own since every upgrade requires multiple of said token. This is why most games make enemies drop money so they can tie upgrades to something that doesn't make me want to pull my teeth off.

The combat is as shallow as a pond too: left click if enemy close, right if far. Healing is just health packs spammed everywhere for 0 reason. Stardew Valley has better combat than this deep slumber inducing bs

And the worst offender:

That ♥♥♥♥♥♥♥ dash.

So atmospheric, enjoyable gameplay, wonderful music and visuals.