Well… if the story is based on Europeans in Italy… and the MC is Italian… and this story takes place in Italy… I don’t quite understand how including characters of many ethnicities as main characters would realistically fit into your story based on the analysis that you just mentioned… Naturally , I do not know what your story is about, but if the main character is depicted as European , and the story revolves around a European MC in Europe… then what would be the reason of racism even really coming up? Unless a LI is of a different ethnicity or something like that.
I guess I just don’t quite understand what you mean to say. But, you probably should not try to include other ethnicities within your story if they do not realistically fit with your story or make your story more complicated that what you have originally intended it to be. Diversity is awesome… but not if it does not make sense or does not actually fit the overall theme of your story.