While you're near Kihei go to Ululani's shave ice, it's on the edge of Kihei and the only shave ice worth going to on the island, they make all of their own syrups out of fresh fruit and have some crazy local flavours too.
Also check out tin roof near the airport, high quality cheap local food, I recommend the mochiko chicken.
If you want more upcountry drive up Haleakala and get lunch at Grandma's Coffee House, the shoyu chicken and kalua pig are incredible, and the one lane road next to is a good walk with some nice views.
If you have any interest in snorkeling it's worth checking out the bay next to the Gazebo restaurant at Napili shores, there are always turtles there. Mala wharf in lahaina is another great spot, there are usually eagle rays and 100% of the time you can find reef sharks in the wreckage of the wharf. IDK conditions right now though.
Yeah Kihei is kind of a dump but there are some nice neighborhoods towards Wailea. I also prefer the upcountry, especially Haiku and Kula. Kauai was very nice in my experience too, unless you get rained out.