I find that strange. We've enjoyed all 7 of the JP movies so far - for our tastes, there isn't a horrible movie in the bunch. Sure, only one is excellent but IMO this series does not drop off nearly as much as most movie series we see. My wife and I rewatched this series recently and we both agreed, this was easily the second best of the JP franchise. We rank the series movies as 1, 7, 3, 2, 6, 4, 5. I can get others disagreeing but I don't understand anyone that thinks this one was worse than 4, 5 and 6.
Scarlett was a draw for me but for us the best part of this movie was the side story about the family just out for a sea cruise. The dad, the two daughters and the boyfriend were terrific.