I've never been one to hold it against a QB if he couldn't scramble. That's a bit of a "bonus" skill in football ... sort of like a pitcher who has a great pick-off move to first base and doesn't give up a lot of stolen bases. It's a good skill to have, but nobody is going to complain about a Nolan Ryan or a Sandy Koufax or a Walter Johnson if they don't hold runners on base very well. Just look at how totally immobile some of the top QBs in NFL history have been (Dan Fouts and Troy Aikmen are great examples of this).
You're right about that. And one of Shula's skills was to make the best of what he had. But I got to thinking. Shula was 2 and 4 in Super Bowls, and the two times he won was when he had a great running back, Larry Csonka, and Csonka was already in Miami when Shula got there. Csonka was a human bulldozer. He didn't require many resources from the coaches or his team mates. He was so tough and dominating that he got unnecessary roughness penalties when he carried the ball.
I don't think Shula ever put much emphasis on the running game except when he inherited one. Once he had Marino, I think any interest he had in a running game was gone, and he wasn't going to take away any of the resources that protected and supported Marino. That got Shula a lot of wins, but he wasn't so great in the post season. And I don't think Marino's stats would have been as good under any other coach.