I don't think that anyone here is arguing that Granato is a good coach. He provided a steady voice to change the culture of the team after Krueger. He clearly helped a number of players achieve higher levels of play. He provided value over the last two years.
I think his fatal mistake is not hiring a more experienced staff. He is a first time NHL head coach, and his most experienced assistant coach is Marty Wilford, who spent 3 seasons as an assistant with Anaheim.
Marty Wilford: 3 years assistant coach in Anaheim, 7 years assistant in AHL
Jason Christie: ~20 years of ECHL Head Coach experience
Mike Bales: 5 years as goalie coach for Penguins and Hurricanes
Matt Ellis: Rookie coach for Sabres
For someone who is struggling to implement an NHL quality system, I don't see how they can come up with solutions internally. The team is not executing what the coaches are drawing up, and I am not confident that the roster, as constructed, will ever be sound defensively. There is a lot going wrong, and a lot of inexperience in the front office, behind the bench, and on the ice.