There has been some stuff on BanPa regarding the imbalance in 4☆ among the girls in Garupa, so I thought I would speak to this issue and show one side of the story:

It is perfectly fine to be disappointed that bushiroad is giving more attention to Yukina and other "mainstream" characters, but they are doing it for a reason. Yukina is the number one character from the number one real-life band, so they were just trying to do it to please their target audience. Because of many people who are angered by the fact that some girls get less attention, bushiroad gave those girls more opportunities (pumped out two Tsugumi 4☆, one Tomoe 4☆, and one Kaoru 4☆ in the past couple of months). I don't think it is fair to Yukina that one would dislike her simply because she is getting more attention, although it makes perfect sense why one would be frustrated that the other girls are not getting the same kind of attention. It takes time but I am sure soon enough all of the 5 OG bands will still have the same amount of 4☆, but it will never be perfect since the game is always growing and changing. I think people should look at the positives of BanG Dream, seeing each new 4☆ as a new opportunity for great stories, beautiful art, and stunning costumes, not as another disappointment in hopes of one of the more "neglected" girls not getting the representation you want. Altogether, it is not fair to base your opinions off of simply how mainstream/popular a character is, it is best to take into consideration their character design, interests, personality, and roll in band to determine who really is your best girl.