And it should be pointed out that a significant chunk of the dialog in season 2 was spent asking if anyone's seen Sophia.
I think it was more than dialog though. Season 2 & 3 were run by The Shield's Glen Mazzara. Since then, the show runner is Scott Gimple, who's previous major credit was co-writer on Ghost Rider: Spirit of Vengeance. He's basically playing a Dave Campo puppet role to Robert Kirkman's Jerry Jones.
Mazzara was a lot better at pacing a season, ratcheting up legitimate tension and paying it off, writing characters that operate intelligently, etc. There's very little drama between characters now compared to Shane/Rick, Rick/Merle, Daryl/Merle. I still like the show but these last couple of seasons are feeling a bit aimless. Gabriel could provide that if he was written well, but he's just there to look wrecked with guilt.
Even the zombies in the early seasons seemed more capable and more human. I get they're falling apart as time goes on, but at this point the group can wade though a horde with nothing more than a stiff arm and a pocket knife.