I've never thought McCallum comes across well in footage. Never met him in person. I think he produced a few very crummy prequels, but he's just that - a producer. Their job is to keep things moving on time, on budget, on schedule, enabling the director to achieve their creative vision while sparing them as much of the logistics and business considerations as possible. His job is not to shape Lucas' creative vision. Even if he were the producer who hired Lucas, once a director is on a show they're captain of the ship. That probably goes doubly so for GL, having created the world, written the script, owning the studio, the VFX company, the merchandising... McCallum doesn't get any credit for his squandered time in the Star Wars universe, but it's hard to realistically lay the blame for those movies at his doorstep either.