Except some of us still like it. Like me. Sure, it's not as great as it used to be, but I call that nostalgia. I don't think Spongebob has declined as much as say, Paper Mario. I still love the show. Yes, it has gruesome scenes and unfunny jokes, but I look around all that and just enjoy the settings and general stories of the episodes. Granted, I don't watch it as much as I used to but that's because our cable is disconnected for my game systems most of the time.
Spongebob was my favorite childhood show, and even if it's declined, I'd rather them make it better than cancel it completely. This movie could actually save the show.
Slightly unrelated to the movie, but I'll just throw it out there that I enjoyed House Fancy (not that scene, but I just usually skip it)