Yep. Gimple never handled Daryl well. Since Daryl is a non comic character lets compare him to the other main non comic characters and how they were handled from season 4 onward.
Beth: Beth was essentially a female version of Billy. She didn't die in the same way that Billy did but she died around the same timeframe.
Bob: Bob did appear in the comics very briefly but he received most of his development in the novel series becoming one of Lilly's inner circle. Show Bob was given comic/novel Bob's background and was given comic Dale's death.
Tara: Tara was also initially lifted from the novels. Her and Lilly weren't sisters in the comic/novelverse but her introduction episode was lifted straight from the middle of the book from Rise of the Governor.
Sasha: Sasha wasn't in the comic but she in a lot of ways took the place of Tyreese's daughter from the comic. Show Sasha was also given comic Andrea's sniper storyline and was given comic Holly's death.
Rosita: Though Rosita was in the comics she at the same time was pretty much a background character in the comic. She was pretty much the designated hot chick that was there strictly to make the tough Abraham look that much cooler. I don't think she really even had all that many lines during her time in the comic. The show really took another part of comic Andrea's story and gave it to Rosita.
Carol: Though Carol is a comic character also the show version is basically completely different than the comic character. And her show personality was largely inspired from comic Andrea as well (they pretty much took comic Andrea and split her personality up into all the main female characters in the show).
There are other non comic characters once we get to Alexandria but these are the main ones.
As you can see for most of the non comic characters in the show they were still largely given portions of comic characters stories. So in many ways even though they were not in the comics they at the same time were not totally made up from scratch and their stories weren't totally developed from scratch.
Daryl though has no comic counterpart at all. He has virtually been made up from scratch. There was/is no character in the comic that you can point to and say that is who Daryl is supposed to represent. And as a result Daryl has become one of the most uninspiring characters in the show since Gimple has been running things.