In general, adapting a myth or a classic story is something that is done all the time. Many, many stories are described as "an updated version of Romeo and Juliet" or "the myth of Odysseus set on a starship" etc etc.
I'm a little curious when you say that the link between your version and the original is "obvious". Do you mean "obvious to anyone who knows the original myth and who will thus immediately see the parallels"? Or do you mean that it's spelled out in your story that this is an allusion to Fenrir? (I think that's what you mean by "it's even explained by tellers".) Like, personally, despite being of Norwegian ancestry, my knowledge of Nordic mythology is pretty slim. The name Fenrir means nothing to me.
But anyway, to my mind, here are the potential pitfalls:
If your story retells someone else's story and doesn't add anything particularly interesting, readers may view it as pointless. Why not just read the original myth?
But if your story changes the original too much, readers may find it annoying. Personally, I really hate it when someone retells a story but turns the hero of the original into a villain or a buffoon. Many recent Hollywood remakes fall into this category. The Mission Impossible movies come to mind: in the original, Mr. Phelps and company were dedicated patriots and freedom fighters, risking their lives to help oppressed people. And they were totally matter-of-fact and humble about it, never boasting of their service to humanity or anything, just doing their jobs. Then the movie made them a bunch of egotistical jerks who sold out their country and their friends because somebody hurt their feelings. Okay, I know they're just fictional characters so there's no point defending their honor or anything, but I just found it annoying. If you don't like somebody else's hero, then don't use him. But don't turn him into a villain.
On the plus side, many readers will enjoy the interplay of a classic story with a modern twist of some kind.