conformist

A conformist is someone who follows the crowd and does what others do, even if they don't really believe it's right.

You might hear someone say that a friend or family member is being too much of a conformist when they're dressing, acting, or speaking in a way that just blends in with everyone else. For example, maybe your cousin wants to be a free spirit and travel the world on her own, but she starts wearing exactly the same clothes as all her friends and joining every social media trend because it's what others are doing. Her family might think she's being too conformist for someone who's supposed to have her own unique personality. On the other hand, if you're at a new job or school, it can be helpful to fit in with your colleagues or classmates by adopting some of their habits and ways of thinking - as long as you're not sacrificing what you really believe in.