I don't think he needs to correct his feet or "platform." I think that's the low-hanging fruit people go for.
Josh has trained the last 2 offseasons to improve his accuracy specifically when throwing off platform. It's all about the hips, not the feet.
And his struggles are mostly mental, IMO. Like Josh himself said, he needs to come off his first read quicker. Pittsburgh and Miami secondaries were able to hold his gaze a bit. It's not about having talent in the secondary, but just scheming it up right, like we saw in the breakdown of the Pitt defense.
Jack Del Rio is another decent coordinator, but I'm not sure he'll do the same things Pitt and Miami did. We'll see. If he simply tries to pressure Allen without adequately disguising the coverage, Allen will eat them up.