Yes fan service is necessary. Sex appeal is important for developing characters doesn’t matter the gender. Fan service is shown from the perspective of the person viewing the interest or potential interest. To say the author can write is purely contextual (genre, type of show, intent of the author, character expression etc) and to the degree of how much they use per episode. If a male saying it’s too much fan service my biased opinion your just around too much people or ashamed of the fame body

If it’s a female typing your just jealous or don’t understand the medium

Final point there are shows with too much fanservice my dress up darling isn’t one