When Ruthie and Simon were very young, they were not treated simply as cute props. They were given their own story arcs, complete with interesting dialogue. The Brino boys are never integrated into the family in a believable way. Their relationships with their older siblings are practically non-existent. Even their parents treat them as if they had showed up one day on their doorstep, with no instruction manual on how to handle them. Early in the show's run, Eric and Annie were depicted as realistic parents making a concerted effort to raise their kids to the very best of their abilities. But they're on autopilot when it comes to Sam and David, to the great detriment of the show.
The show kept rolling along through this ninth season (and two more after it) because the loyal following was so used to spending Monday nights with these characters. There just wasn't much left to do with them. Time gets spent on characters like Martin (Tyler Hoechlin), the boy who became a permanent resident at the Camden household a couple seasons earlier. Martin's father is a Marine stationed overseas and his mother is deceased. So he invited himself into the Camdens' home one day, eventually becoming practically one of them. He's not a very interesting character, in fact he's extremely self-righteous. His romantic life, and Ruthie's growing crush on him (now that they're both in high school), is a recurring distraction throughout the season.
Packaged in a standard keep case, as with the previous seasons, the five-disc set is presented as simply as possible. The case is the same width as a single-disc release, making it a very economical for storage purposes. The audience for 7th Heaven: The Ninth Season is clearly those who have purchased the previous eight seasons. If you own all of those, there's no sense in stopping now. But I doubt many new fans would be earned by starting with this season. It sputters along in search of a strong arc, but never really finds it.