In what way is Malzahar GENUINELY okay?

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His W is the same spell class it used to be before when it was his passive, so he has no additional single yarget spells, and he could use it without his ultimate before.

Given that his old W is now tied to a single target spell he lost one of his AoE spells, his new passive also is not a single target spells so he lost an AoE spell to gain a spellshield, therefore he's more single target focused than before.

Lockdowning is a specific type of passification in which the target is roughly immobilized. Originally Malzahar is a passifier with one lockdown spell which is his ultimate. Generally, his spells are oriented towards passification since he wards of enemies with his damage level and continuity and affects them.

The cooldown on his Q and W got reduced by a lot (-3s on Q, -6s on W) so he can still ward off enemies by using Q and letting the W Voidlings deter enemies from simply walking at him, the damage on Q may be a little lower but it still hurts squishy once he has some AP, same for W even though it lost %max health damage it gained a .2 ratio and some base damage.

In compositions character is important in deciding correct hero's, in this case damage over time is required for applying high amounts of damage without precise speed.

Yes, but Malzahar is not picked because he brings DoT to a team, he's picked because he can push fast, brings a silence and a suppression and has a spellshield to defend himself.

He's a high damage wizard who controls targets and engages them over a period

Yes, even though later in the game he doesn't need to wait to R someone since his team will bring all the damage.

Lockdowning is a specific characteristic of his skill and not descriptive of his whole character, and anti diving is also a limited skill also dependent on his ultimate whereas he has far greater powers.

His all character boils down to a spellshield, a long-medium range silence and a suppression, his E and W now are just what he uses off CD on enemy champion who get into range, his E is still iconic to him but it's in no way an important part to how he plays in a teamfight, he just peels his ADC and himself, his E is just a generic magic damage over time spell when used on a champion, his W almost non-existent ourside of lane.

Also, if you're talking about current Malzahar, I didn't see the word cancer.

It's not like the old Malzahar wasn't cancer to play against, it just wasn't a braindead balance mess like this one turned out to be after a guy with 7 games on him decided to reworked him.