there's a combination of things. at a very surface level, we can consider how she doesn't have a strong cp which matters a lot in the river rn (also her bp4 partner left the river, while her maybe-gf is graduating soon). but she's been here for a long time, so it runs much deeper than that. she's not popular because she rarely gets opportunities, lines and screentime, and that is born out of not ranking (and when she does, her performances are not consistently outstanding). but why isn't she ranking? because she's not popular. sys doesn't have the sort of personality that easily catches others' attention, but this is born out of her destroyed confidence. why was her confidence destroyed? sys knows that she isn't the best performer, but she tries her best. however, despite her best efforts, she wasn't able to learn as fast as the others and the more she fell behind everyone else, the less confident she felt. this has been an issue since her bej days, but has gotten significantly worse since then. back in bej, she felt that she could still have fun even if she's not that good, but she doesn't have the same confidence to put herself out there anymore. i think it's getting better though and her performances are also getting better (so please pay some attention to her!), but there's also this thing about how she gets no opportunities and is always in a corner, which means people don't really pay attention to her and it's hard to gain popularity. contrast this with other h2 xox who might have successful cps or confidently put themselves out there on stage, it's easy for sys to fade into the background. so yeah, maybe this whole answer kinda boils down to "sys isn't popular because she isn't as good as everyone else" which sounds unfitting of someone who is her fan, but i'm saying it as i understand it. i won't pretend she was born a stellar performer or anything, but i want to say that she's someone who works hard and really loves the stage, so she is as deserving of recognition as the others

so anyway tl;dr is that my girl has not graduated from nugudom in her life. she just basically never experienced a break which resulted in enough fans (to help her rank, etc.) to attract more fans