As far as I understand, the forward positioning of the engines makes it so that the plane tends to pitch up when it is already pitching up, and tends to pitch down when it is already pitching down. This is the definition of an unstable system.
MCAS compensates this by trimming elevators. Without MCAS, it is up to the pilot to handle the unstable system.
MCAS compensates this by trimming elevators. Without MCAS, it is up to the pilot to handle the unstable system.