There is a Huge Difference between Wonhee debuting in Illit and Sakura being chose in Prelude (Saint Satine)
People should stop comparing and using Wonhee debuting in Illit as Justification for Sakura's debut. Both of their situations are completely diferent.
(DISCLAIMER: I do not hate Sakura. I actually feel sorry for her, given the amount she is facing/yet to face at such a young age. Also, this is NOT her fault. It is completely HxG's fault. I am not hating her, merely criticizing. Plz do not give hate in the comments)
First of all, I think is the biggest difference and what affects this most. Wonhee was chosen AS 1 OF 6 GIRLS TO DEBUT while Sakura WAS THE ONLY ONE, THE FINAL PIECE. You're telling me, out of 14,000 girls; they could not find a singular perfect polished trainee??
Next we go to the background. Sakura is debuting with 3 other people, all in their twenties and who have been training together since Dream Academy. While Wonhee debuted with people her age and they were formed together. This will eventually lead to Saint Satine's chemistry being a more business-like one (Not the girls' fault TBH) while Illit did built their chemistry from the scratch.
I think this is what is going to affect Sakura the most. She will have to learn a completely new language while Wonhee debuted singing a language she had pre-learned.
Last but not least, Sakura cannot sing. Wonhee had a natural singing ability (Of Course, there were other girls in the show who could sing way better). But comparatively, Wonhee is very very ahead compared to Sakura in singing.
Wonhee also fits the group concept perfectly. She is the face of the group and she does suit their dreamcore concept. Meanwhile, Sakura does not match the other girls' vibe (Seeing the recent appearances).
Also, Wonhee during the show, was very popular in both Korea and Japan. While scouring the internet now, I saw most people in both countries wanted Ayana to debut.
Honestly, HxG did not think this through. Ayana in my opinion, was perfect to debut.
NGL, I feel bad for Sakura. Imagine having to learn a new language and that to be in a group who have known each other for 3 years and are friends and on top of this, face overwhelming hate for not matching the other 3's skill level.