@knuspi The rating and reviews will display using your theme’s fonts provided that you don’t select one of the “… with Fonts” themes.
If you want to use “Poppins”, please ensure that this font is properly loaded into website’s front end. For example. you’ll need this set in your theme or manually added to the Custom Styles or your preferred style sheet:
@import url('https://fonts.googleapis.com/css2?family=Poppins&display=swap');
This is an example, more details can be found at: Google Fonts | Poppins.
If everything is set correctly and the font is still not being applied – can you check that there are no error message on saving the Custom Styles? Also, please remember to clear your cache (if this is installed and active).
I can assist further if you send me a link to your website.