Don't get me wrong I love Jihyo's voice. Great volume and power. But some say she's over-trained for KPOP. The poor sis had already trained for 10 years (with Miss A) before SIXTEEN. She'd do so well in broadway or something.
Naeyeon and Jungyeon are no doubt great main vocalists. Mina and Sana can hold a tune and have very pretty and distinct voices. That's important for Kpop. Koreans don't like to listen to belts and screams.

Range that spreads more than two octaves is kinda pointless for Kpop.
And Chaeyeon is a VERY capable rapper. Watch the bold woman performance.
Tzuyu, Momo and Dahyun are bit

in the vocal/rap department but they bring other thing to the table (visuals/dancing/variety/controversy). I would say they play a more important role in TWICE or would in any gg than a good vocalist.
TWICE is a very solid group and y'all will deal.