Agree with Mithrandir, If you want to avoid cliche, you would ultimately have to create your own fantasy creature, with their own realms and beginnings, languages, foods, etc. Most fantasy stories revolve around elves, orcs, goblins, humans, because these are creatures that already have a world created. They are familiar, if you say an orc, 9/10 fantasy readers will know exactly what it is and can visualize it. To avoid this while still being fantasy, you would have to do the work to create new beings which could run the risk of being too unfamiliar. If they struggle to relate to the species, if they struggle to comprehend them, you run into the risk of losing reader interest. That's why the typical set of creatures are found in all fantasy styles. They are established and proven to work. Each species has a personality that people can relate to. Orcs are your meathead warrior jocks. Elves are your refined, civilized species, hobbits are your party simpleton species. Goblins are your thieves. They all have a certain personality trait that people can relate to.
If you are looking for fictional medieval, you just need to create humans and create your own world not related to earthly locations like middle earth for example. If you want to start adding in goblins and orcs, it's going to be cliche and up to you on whether you want to do a typical romance style fantasy novel where a group of heroes fight against vast armies and come out victorious or apply some realism.
With that being said, to make it authentic or not would depend on the story/world you want to create. The types of creatures and species doesn't make it any more or less authentic because they are all a part of the authentic fantasy realm. Up to you to create the story with the said species and creatures to create the cliche story or create something from a different angle.