Both have unreal visuals but aren't popular due to lack of strong personality and idol skills.
This isn't a shade btw, I am like that also, you can't change your personality. But it is just such a shame that they weren't able to achieve bigger heights.
Your personality is definitely lacking, but Tzuyu's isn't. And skills? She's one of Twice's lead dancers. She has lost the immense popularity she used to enjoy because of JYP, who is afraid of letting her do anything for fear of losing... whatever the hell it is China provides. She's a victim of bad politics, plain & simple. I would expect an actual Twice fan to already know all this, hence why I find myself having to explain it to you.