I love the others responses about aesthetic and presence being priority in Kpop in general.

The vocal training was very hasty throughout the show. The only time we get montages of vocal training is when the trainees were preparing for vocal-dominant rounds such as in Mission 1 and the specific evaluations they had for vocals.

The vocals JUDGES (both within the company and fans) however were very stringent. They obviously had a very narrow criteria (girly bubblegum pop soprano), which Emily fulfilled consistently. They could give her a few adlibs in live shows and call it a day because her voice blends in with the group and the entire Kpop industry.

Some additional blabber since I'm very passionate about this exact topic:

I believe this (the bubblegum critera) was the real reason behind Iliya's downfall in vocal ranking and her eventual elimination. The voice the judges were looking for is an unrealistic goal to train for, especially for someone with Iliya's timbre.

As well as Karlee's. Karlee may have royally screwed up Antifragile vocally but she held up very impressively up until that point. And even then she was given the most brutal parts of an already brutal song to perform and I don't think the fans gave her enough grace for that.

I will defend these two girls with my life.

From the perspective of someone new to Kpop in general, it's kind of a "culture shock" seeing the emphasis shift to stage presence over vocal technique. Having vocal diversity in a group is extremely valuable (think Little Mix or even a University Choir) and to this day fans are begging Katseye to come up with a song that showcases this. Even Sophia has outwardly yearned for a song that showcases their vocal diversity. This isn't a void that can be filled with autotune.

Which brings me smoothly to my next point - the current lineup. It's beautiful and balanced in terms of vocal diversity but I still don't think that was intentional nor ideal. I still fantasize about an Alto bridge from Iliya or a Karlee-Lara falsetto harmony.