Yeah I wasn't crazy about this season either. The basic idea
was a good one I thought, but I was just never able to buy Stiles as that character, and I never found the Jordan Chase character remotely threatening either (at least the lackluster Season 3 had the physically imposing Jimmy Smits for a villain).
And then you have all the contrivances, such as Quinn deciding to ignore very
incriminating photos of Dexter and Lumen just so he can be with Debra, or Liddy conveniently not witnessing more than he did.
And by this point, Debra is just starting to look like a complete idiot for not at least having a SUSPICION about Dexter (and despite what others are trying to read into the finale, I still don't think she does).
My biggest problem though is that Dexter himself has lost almost all of the edge
he used to have. Perhaps it's only natural that he slowly become more emotional and human as time goes on, but it's that dark, slightly creepy edge that made him so compelling in the first place.
I miss the cold, emotionless killer of the first couple seasons who had to put on an act wherever he went. Now he's just another bumbling dork who sometimes says the wrong thing at a party.