A "style rut" refers to when someone becomes stuck or bored with their usual way of dressing or presenting themselves. It means they feel like they lack variety or creativity in their personal style choices. Full definition
It's not wrong to feel in style rut and be dissatisfied with the core items in your wardrobe - because this is only the beginning! (style-yourself-confident.com)
This post is so inspirational, and such a great way to get out of my winter style rut. (thefashionfolks.com)
I was in a decades - long style rut with business clothes, but am now retired and busy trying to reinvent my wardrobe. (unefemme.net)