I think there's starting to be some confusion here of two different arguments -- the first argument being, "the anthro element should serve the story in some way," and the second, "there needs to be an explanation of how the furry characters came about." Those are two different concerns. The first is a "why" sort of question ("why are there animal characters being used in this story?") and the second one is more of a "how" ("how did there come to be animal characters in this story world?"). The two concerns may be related sometimes, but the "how" is not always important. The "why" often is, even if it's not directly addressed in the story text itself.
I think there's starting to be some confusion here of two different arguments -- the first argument being, "the anthro element should serve the story in some way," and the second, "there needs to be an explanation of how the furry characters came about." Those are two different concerns. The first is a "why" sort of question ("why are there animal characters being used in this story?") and the second one is more of a "how" ("how did there come to be animal characters in this story world?"). The two concerns may be related sometimes, but the "how" is not always important. The "why" often is, even if it's not directly addressed in the story text itself.