It depends on what you mean by "great." I don't think this offense is great at this point, do you? Very good, balanced, efficient at times, but not great. And that's just my point. With two and possibly even one top receiver, this very offense has the potential for true (like historical) greatness. It has the offensive line, the back, the tight ends, and certainly the quarterback. All it lacks (putting aside the coordinator) is at least one elite wide receiver. They wouldn't need to score on every drive, just one or two more times a game than they are now. That is what I mean by Beane letting us all down by settling for Shakir and a bunch of backups.
I get it, he has a lot of holes to plug on defense. I don't even blame him, really, although I think a historic offense could just outscore everyone. But it's a bit sad to think what we're missing.