It's like some people don't understand delegation of authority.
I had a guy working on a graphic for me. He's not delivering. I'm the one calling the shots, he's supposed to do what I tell him, but here's the impasse. He can do what I can't do, and he won't do what I tell him to do. My resolution is to move on to someone else, which is exactly what Saban did.
He's not running the offense, even if he was an offensive coach, it would still be pretty rare to see him running the offense. So yes, all he can do is try to get the coordinator to run the style offense he wants, and in the manner he wants it. He's not at all in a position to sit down and draw up the plays, and then see to it those plays get called. Furthermore, there's a mile of difference between Saban knowing what types of plays he wants run, and drawing up the exact plays. The offensive coordinator is paid a lot of money to do that. I know what the graphic looks like, but I don't know how to create it myself.
Saban has to delegate, in regard to a lot of things. Sure, he interviews and hires a coordinator, but are some people here serious? You all know how the hiring process works, you never really know what you have until the person starts working for you! We've seen play calling questioned, we've seen Saban blow up on the sidelines, so this talk about oh, well I don't understand why he didn't do more or what not is silly. The coordinator is gone, he's been replaced, and Saban clearly wasn't happy with some of what he was doing. What else did you expect Saban to do? Fire a coordinator mid-season, cut back on recruiting and all his other duties and become offensive coordinator?
Edit: I'll also reiterate something I said at a few points last season. Saban wasn't able to take any real risks. He had to keep putting patches on the Alabama program. He has a lot of attrition, coaches leaving, players leaving, but he was on a run and very nearly a modern record. He had to keep trying to match his coaches with what he was doing the previous season, and match his players with what he was doing the previous season. So, yes he might not have been happy with the offense, he might not have been happy with the coordinator, but he really had limited options. Hiring a new coordinator, installing a new offense, that's a big risk.
I don't really know why people hold Saban to such ridiculous standards. Apparently he's supposed to run the offense in addition to everything else, while never losing a game, and I guess he has to take over scheduling and schedule nothing but tough games (which to reiterate he's not allowed to lose). Yeah, sure...
If you don't understand Saban's complaints, just read some of the posts here from alleged Alabama fans. You'd almost forget he won three national championships at Alabama.