IMO, this is always going to the slippery slope argument to the point where nothing would ever be a satisfactory answer.
Just the mere act of having Humans portray non-Humans will bring up any question of authenticity, and even if 99% of the audience is okay with it, there'd be some 1% jumping on the forums making a stink at how some detail isn't exact to how Tolkien envisioned them to be.
Even if the Black skinned Elves and Dwarves may seem egregious to the source material, at the end of the day it doesn't even matter. Cuz we could just as likely be looking at how poorly translated the Orcs and Goblins are in being adapted as two different races, or how the Wargs don't ever talk in the movies, or some other banal shit that doesn't really matter. Like, Uruk Hai were never meant to be man-sized, yet the depiction in the movies is fine for what it is. The creative liberties don't get in the way of enjoying the fiction unless it breaks your personal suspense of disbelief; and that is going to be different for everyone.
It's all splitting hairs in the grand scheme of things. What really matters is if they have a good story to tell and whether they are able to tell it. Whether it is canon or fan fiction is really up to the individual to decide. Cuz at the end of the day, I'd like to think we're all mature enough to decide whether 'Han shot first' for ourselves. It doesn't matter what the internet thinks at large, it doesn't matter what the corporations decide as being authentic or official, it only matters what we view for it ourselves. If the creative decisions break suspension of disbelief, then it is going to be a matter of personal interpretation and expectation, and little else beyond that.
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Absolutely splitting hairs.
There is no rule that an adaptation or derivative work can only use the brand name if it contains a certain amount of source material.
"Star Wars: Visions" is a completely fictional series of non-canonical work that has the Star Wars branding to it, regardless of how much source material is used in each episiode, in each self-contained story and universe. You're literally just projecting here.