Azir is still hilariously underpowered as far as dynamic goes, but the main reason he's at a 39% winrate right now is because he's free play this week and people are trying Azir out for the first time and just getting helplessly slaughtered.
What people bitch about with Azir isn't his strength, its his irrationally, head-slammingly, frustrating laning phase. His safety combined with his relatively high damage for poke makes him a nightmare to lane against without someone who can match his range. If you're playing a melee mid-laner other than Kat or Zed, just keep your towelette handy because you'll need it to mop up your tears. Combined with the fact that so long as he has mana, he's virtually ungankable and unall-in-able, you have yourself a champion who is the source of a lot of salt.
Beyond the laning phase, though... Azir is just pathetic. He's one of the weakest champions in the game when it comes to post laning phase. His teamfighting is usually lethal with a good frontline because he's on par with squish levels of Anivia and if you have a lacklusted frontline or no frontline at all, then good luck doing anything in a teamfight other than throwing down your ult for a little bit of peel when the enemy assassin dives you harder than a yellow submarine.
Azir dies... SO FAST... and it's not like it's actually hard to catch him, either. His defensive cooldowns are his offensive cooldowns, meaning if he has to use them in a teamfight, he might not have them up when he needs to... you know... not die.
Making an impact in a game as Azir is all but impossible without a lot of team coordination. There's a reason why he's a god-tier mid laner in professional team play and sort of a joke in regular ranked play.
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It deals decent damage and applies a slow. It makes you careful about how you play, although I do think Malzahar with Rylai's might be actual cancer