I'd disagree with about half of that evaluation.
Rudolph has a good arm, and is plenty accurate. I agree he has very little mobility, and is slow to process reads, though that is not uncommon for inexperienced QB's, likewise for pocket awareness.
He's not a world beater, but he has shown some ability and some promise. He's also been working with very little healthy talent around him. Not that you are doing it, but many are holding him to Roethlisberger standards, and that was always unrealistic.
He always needed seasoning, he came from a very unique college offense, but I'd still call him an interesting, though lower ceiling prospect. My pre-draft comparison was Matt Schaub, or Brad Johnson if you wanna go back a ways, and I haven't seen enough to dissuade me from that yet. Those guys took time too.
I'm certainly not saying Rudolph is a franchise QB by any means, but I'm not ready to ship him to the XFL either.