the show is starting to lose it's .. "spark". i guess if you wanna say that. it's been losing it since mary and matt left. it's not the same. and i don't know if you guys watch it, but simon left too. that just leaves people are aren't in the family like ashlee simpson [she's a complete idiot for doing the show, and well, her sister ..., oh and her annoying voice]. it's not the same. ruthie, the youngest sister is like a psychologist with every answer. it kind of bugs me because it seems like she can never be a little kid instead of trying to be so grown-up. and there's lucy. she's the only one that's the same from all the kids that left. i used to really, really love the show ever since it started. now it's just drifting off. that's kind of sad.
It is inevitable that this sort of thing happens. This show started out as a show about a particular family and all the members. Once those kids grow up, though, the issues change and so the show can't stay the same. However, since the show isn't supposed to be about a family of adult children, something has to be done to bring in young children again. Unfortunately, this doesn't have the same dynamic because it is a different bunch of people and the chemistry isn't the same. In addition, these other kids aren't family so, the investment by the parents isn't the same. What has happened is the cast outgrew the show and the network doesn't want to cancel it right away because it has been so successful. If the new format isn't successful, it will end up cancelled which is probably what should have happened at the end of last season.
I love this show and still watch it, but it isn't as good as it was in the early seasons for the reasons I listed above. In my opinion.