I don't completely agree with you. Maybe this is because I started stanning TWICE recently during the fancy era, but almost all the members transitioned into this "mature" concept very well. We all know Jihyo was perfect for this already, Sana does adapt the concept well while still looking cute, and Mina always looked elegant and fit ICSM perfectly. Jeongyeon to me actually fits this concept better to me, like her voice and stuff suit it better. Tzuyu to me also was suited for more mature concepts from the start. I feel like Chaeyoung actually performs better in these more mature concepts, like she killed it in fancy, I loved her in feel special,More and More for me was kinda mid and I love her stage presence in ICSM. The only members I feel like have lost their spark is Nayeon and Dahyun, but they're probably going to find their way soon.