I think he loved Rita, but knew he could never trust her with his secret.
The original Dexter character misunderstood himself as feeling no human emotion. That was Crazy Daddy's script for him. But pretty much every scene outside of the kills contradicted this. This Dexter loved Rita as best as he could, making an admirable and endearingly comic effort to live up to his self-imposed obligations.
The new Dexter character may say and believe he loves another one but I really don't believe the new Dexter character actually feels very much, if anything, in the rest of his life.