Ehrm you must not have not many ZvPs lately in the GSL, because all the trend now is ling infestor into muta (which is actually a brilliant follow up,). Although I have no idea what was with the numerous amounts roach baneling busts yesterday lol.
I don't like the Neural nerf, it's ignoring too many problems with Zerg and the infestor but to claim that no one is using the infestor is absurd.
However, Korean Zergs besides Coca are absolutely goddamn awful with infestor control, and I don't believe that KR Zergs are that experienced with infestors. Watching DRG v Losira was while epic, saw so few usage of infestors properly, they're too passive with them, Losira and DRG could have used Burrowed infestors + IT many times but Losira kept on using roach flanks while DRG kept on going for a roach bust, it essentially boiled down to roach fungal v roach fungal. Although DRG did finally use Infested Terrans to clear Losira's 4th. Destiny has much better infestor control and I think understanding than both of them :/
Coca is someone to emulate though, his infestor based ZvP is pretty godly and I think he has the best understanding of where infestors lay in the Zerg arsenel.