I think it's actually really simple: Daisy isn't all that prominent a character, primarily existing in Party or Sports titles to expand the female roster. She doesn't headline her own games like Mario, Luigi, Peach, Donkey Kong, and Yoshi all do. Toad is an omnipresent fixture in most Mario-centric titles, so he kind of exists in his own lane.
Not knocking her. Daisy's spunky personality is a fun counterpoint to Peace's relative tranquility/stateliness, and it looks like she will get more of a focus in the next Mario film, which could in turn lead to more of a park presence. But for now, the park has limited bandwidth and resources for meetable characters in Super Nintendo World, and they're choosing to prioritize Peach, the more recognizable character that most guests would prefer to meet over Daisy. I do think there could be more merchandise for her, but again, she just isn't all that prominent outside of certain gamer circles. Her inclusion as a Power Band I think just speaks to Nintendo's desire to include a second female option.