I'm such a flower lover, it's hard to come up with any I truly dislike completely. I have never become a big Daylily fan though. Having said that, I do find some useful in the garden and nice combined with other plants, and among those do have a few that I wouldn't want to be without. I do have a dislike for the orange ditch lily species because they're downright invasive in my rich soil, and Stella d'Oro because I'm not big on the gold color and they're so common.
There are others I used to dislike, but have had a change of heart. Coneflowers is one, for the same reason Lucy mentioned- they just looked like a dying bloom to me. I started growing some to harvest for tincture, and have enjoyed them, especially since they're a butterfly magnet. Since then I've tried a few modern cultivars.
Even being an Iris enthusiast, I used to dislike browns, seeing them as dead looking. Nowadays I'm coming around to like them, just like to see them combined with complimentary colors and away from bright, clear colors.
