I wouldn't call it bad writing. At all.
Hobbits are central to the story and has been since its inception. It's weird saying they did nothing for the show when aspect of the characters are there to world build
Infact, the Harfoots specifically are laying the ground work to why Hobbits are how they are. No one leaves the trail=equals no one leave the shire. You see a race that was forever on the move suddenly settle in one location. Why?
You cut out their story and you lose the interaction with the wizard who if it is Gandalf builds on why we see him so engrossed with them by the time we get to Frodo. And yoy can not sat Gandalf is boring or not needed to the story
Maybe the Harfoots were to slow/or boring but the writing on them have been astounding. We've seen traits of Frodo, Merry, Pippin, and Sam in that entire Harfoot society. Thats brilliant to me