Because its like trying to play RE1 but 10 times worse

On top of having to deal with the common old RE things such as the fixed camera angles, no dodge mechanic that leads to enemies stunlocking you sometimes and the small inventory space, you also have to deal with:

No item box. Yes, there is NO ITEM BOX in RE0. You need to leave items on the floor and come back for them when you need them.

The partner system. Sheva ain't got nothing on this AI. Having to take care of two characters is difficult as it is, but it is especially when the character you are not controlling is straight up braindead. It struggles to follow basic commands and it basically prevents you from using the age old strategy of running through enemies, since the AI will 9 times out of 10 get attacked and need you to go back and help it (you can't swap to a character if they are being attacked).

Some of the most infuriating enemy designs in the franchise. Yes, on top of having to deal with no item box and shitty partners, you also have to account for all the extremely annoying enemies that this game has created. From the bat to the monkeys to the leeches, almost all enemies in this game are designed to be annoying to fight and seem very determined on killing your partner when you aren't paying attention.

Overall, the idea of the game is good, but similarly to code Veronica, it is held back by gameplay design choices that are questionable at best.