It is indeed a pity that Sejeong's singing career floundered since her Produce days, gugudan made good music, but gods did not smile on them. Unlike Yeojeon, the other IOI vocal powerhouse who thrived in WJSN.
Her solos, well she got 2 music show wins. Flower Way got to Gaon #2.
Otherwise nothing much to write home about. Her popularity is more from Variety-TV, CFs and dramas - pretty successful at those.
She is an impressive vocalist- many duets with veteran singers, musical theater etc. but not a smooth dancer, By her own admission, dance does not come naturally to her. She has to put in a lot of work for that, so her songs are highly reliant on vocals. Which is not a great market, unless one is IU.
Unlike Eunbi, Yuri, Yena - other "less" dance based singers - IOI did not have a fandom built like Wizone to support going solo.
So can she really redux on the singing/dancing K-pop career?
If she/Jellyfish keep going to folk like Sungwoo Jung A for ballads, nothing much is going to happen.
I doubt it though. She can be a Gummy or maybe Ailee type, OSTs etc., And multi-field success would help with that.
Which is fine, not every song needs to be dance-bop.