Fails as a princess: during season 3 (and shortly season 4) we begin seeing Star trying to change her behaviour, develop as a character, which is great! It is a good turn from her, and we somehow can guess she won't be capable of doing it, when I watched the episode where she can't even decide what will breakfast be I felt it was obvious because she never really cared about it to begin with, from being a princess that never listened ti her mom Star went to being a princess that never heard her teachers, the Diaz, her best friend Marco, she 99% of the time paid deaf ears to anything she considered unimportant, even though it was important.
Star in a certain way was meant to not listen to her mom, Moon, because she feared she was gonna become "boring" or stiff like Ms. Heinous.
She also fails there because she always looks for the escape, gaving up the kingdom was one of her worst decisions, even under the condition of "giving it to Eclipsa" because she had already given it up as well before her, even abandoned the wand! The only thing missing on that story was Star realizing that Eclipsa was too selfish and didn't care about the kingdom or general well being of others, but herself, but since the people in charge of the show turned Eclipsa into a "too good for the world", they couldn't just make her appear as a bad person, so they never did that episode, but I guess many felt like that was probably what they were aiming at.