it needs one [collision box] because it's a KinematicBody
A KinematicBody does not need an attached CollisionShape. It just won't be able to collide with anything without one. Other than that it will work just fine.
tried to change [the player's collision shape] to a RayShape2D. Though, the player just glitches when he reaches the enemy.
What do you mean by "just glitches"? What exactly is happening?
Without knowing more about your game and what you're trying to achieve, it's hard to give you the answer you're looking for. You could replace the CollisionShape2D attached to your player with three RayCast2D-nodes pointing up, left and right of it. If one of them collides with an enemy, you'd stop the movement. As there's no ray pointing downwards, the player would still be able to fall through enemies though.