Marksmen junglers being prevalent has a lot to do with it. Your ADC and Jungler benefit greatly from an Azir wall in a teamfight. If marksmen junglers weren't so good atm (literally was just Graves / Kindred at MSI), Azir would not be the contested pick that he is. Yet he's getting nerfs because Riot doesn't understand that champions can be strong in one meta and be useless in another. Basically they take as many ranged champs as they can, and his wall causes them to win the teamfights. It's not a thing with Azir himself, the problem is actually ranged junglers becoming a popular thing.