Do it for her!
Why do I like Cure Scarlet?
Go! Princess spoilers ahead! I've tried to keep it as spoiler free as possible, but it's difficult to go into detail about why I like her since that requires delving into spoilers. Click to reveal!
Simply put, I vibed with her character a lot. She really inspired me. I liked that even though her childhood was kind of sucky (to put it mildly) and even despite temporarily "losing" things important to her, with a little push from Haruka, she decides to "never despair" again. She then learns how to laugh and smile again, thanks to Kirara. Then she learns to face her fears thanks to Minami.
In other words, I found it really empowering how she went from feeling like she was nothing, to being something. (And she has also inspired me to want to learn the violin despite not being musically inclined in terms of playing skills.)
Additionally, as a villain-to-Cure character, I think both "versions" of her character are interesting! As Twilight, a villain, she seems like a representation of the negative things associated with the title of "princess"--she only cares about status and is mean-spirited and snobbish. However, after being restored to her true self, Towa, she becomes Cure Scarlet who, to me, represents what a "princess" should be; someone kind and strong that you can look up to, who's also kind of just a normal person/friend like anyone else.
Her debut as a villain and her debut as a Cure both left a huge impression on me back when I was first taking an interest in Precure and thought no midseason would ever top La Mer's debut. I kid you not, I was crying when she gave her speech before transforming, and then her first fight? Ah, so well animated and choreographed.
She's just a very silly and charming character with a really banger design. I usually dislike the color red and its variations, but her design just uses it so well. In short, I just think she's neat!