The problem was his training with Mihawk. The author had a hard time trying to write for him after that, and still fit Zoro into the story. If he had a different mentor for those to years, he could've done more each arc not only in Wano but leading up to Wano. Zoro has been boring since the Timeskip.
Definitely not zoros arc, it should have been, but it wasn't. My guess is that we'll get zoro backstory and character development right before/ during his battle with mihawk. I'm sure there will probably be some wano tie when that happens, I'm also leaning towards the idea that we'll come to learn that zoro is a shimotsuki and how those from shimotsuki village ended up leaving wano and going to the east blue. I also find it somewhat likely that zoro will end up with another sword made by shimotsuki kozaburo who forged Enma, Wado Ichimongi, Ame no Habakiri, as well as the first two lower grade swords zoro started out with and received from shimotsuki kozaburo himself in shimotsuki village.
I find it fairly likely that shimotsuki kozaburo was zoros grandfather but kept that fact a secret after fleeing wano from kaido since that was considered a disgraceful act similar to how Kozuki sukiyaki hid the fact that he was momonosuki's grandfather because of his disgrace after kaido conquered wano. If that's true that would mean zoro is a decendant of Ryuma, as well as a cousin of Yasuie and toko. But as I said I don't expect us to learn any of this until zoro gets his rematch with mihawk or possibly until the crew meets dragon who could have possibly helped the family escape kaidos rule, although I don't find that scenario quite as likely as the rest of this theory.