Nerfed to stupidity. Can no longer Jg. Useless as support. Can't compete with Midlanes or toplaners.
HAS NO LATE GAME SCALING. Incredibly squishy. No escapes. Shield pops with 1 AA.
Completely defenseless vs late game ADCs
Malz himself had his base move and AA range nerfed.
The list of nerfs goes on.
The problem with Malzahar is that people who can play him, play him pretty well, and it skews the whole damn thing. So then you nerf the crap out of him and now he's useless.