I know someone that has played for and against a Sirianni team and actually worked with the Eagles during the draft last year. I'm not a big Sirianni fan, but he talks very highly of him. He has hinted what he thinks is wrong with the team and doesn't think it's coaching, but with execution. He won't elaborate on players. If it's execution, then I tend to think it's coaching.
All that being said, has Sirianni ever called plays? Doesn't the HC usually step in when the plays aren't working? I get the hands off approach, but at some point you need to step in.