Kauaʻi is the scenery island. There is no ring road and no road through the interior, which is why the Nā Pali Coast has to be seen from a boat, a helicopter or on foot, and why the highway simply stops at Kēʻē and Polihale instead of looping.
That wildness is the whole appeal and it comes with trade-offs. Fewer restaurants, earlier nights and rain. The interior is one of the wettest places on earth. Plan for a shower most days, plan the north shore around the weather and it becomes the trip people remember longest.