Putting aside that long and unnecessary tangent about Twice

I don't think you understand what we mean by childish
Cute≠childish
Pop≠childish
Nonsensical lyrics with basic, gibberish choruses overusing aegyo that sound like reject Disney OSTs=childish
Something Red Velvet is guilty of almost as much as Twice
Twinkle Twinkle: childish Darling: definitely not
TT: kinda childish LOA: Not
My Super Lookie Lookie Rookie, Go Go Airplane Ba Na Na Ba Ba Ba nananan, zimzimzalbim,& Umpah Umpah: All can be considered within the realm of childishness as opposed to ICC, RR or DD
Whether they pull off or not is up to you, Twice bashing isn't going change that
I can get Sones having their fair share of issues with Twice and Onces, not gonna deny that I had quite a few myself but their concepts should definitely not be one.
That's a direct slap in the face of Soshi who, by your logic, would be considered 1 dimensional. When SNSD was at the same point that Twice was in their career, they were still releasing music even cuter and girlier than Twice and continued to do so throughout their career.
Bubblegum pop was still their signature sound in Korea until 8 years in when they graduated to
color pop, aka what Twice is doing now
Twice is experimenting and gradually changing their sound. They will be just fine