Been a fan of fantasy with elves from Tolkien, Witcher, countless fantasy series and games and the extreme deviation just pull me out of it.
The crux of it is that "Elves" are unique to their setting.
While Tolkien is the major reference used for modern fantasy writing, it is not the end-all-be-all.
Races exist uniquely in each setting. Sure, many tend to copy Tolkien's designs. But not all do.
In Divinity, elves are different to Tolkien's. They're much more elongated (Though technically, that is also how Tolkien depicts them too. Peter Jackson's film takes a lot of liberties with the source material, elves being just "Sexy humans with pointy ears" is one of them) and have different cultures. Especially in regards to death, with their trees and the whole "Obtaining memories through eating body parts" thing. The only thing Tolkien and Divinity elves really share is the whole "Created by a god to populate the world" backstory, which is more coincidental than anything (Divinity doesn't have the same subplot background regarding Eru Iluvatar and the Valar)
This means your comparison with Star Trek and Vulcans only makes sense if the media in question is based in the Star Trek universe and is specifically using their form of alien species of Vulcans from the planet Vulcan, the highly emotionally volatile race that uses meditation to quell emotion in order to maintain a logical clarity.
If someone is writing media for say... Harry Potter and they choose to have a race of "Vulcans" it doesn't mean they have to be at all similar to Star Trek's Vulcans simply due to them sharing a name. They can be completely different, because it's a different universe and so they're different races.
Speaking of Harry Potter... They are an example of elves being portrayed completely differently to Tolkien's. Them being short, impish creatures that have little to no hair and a penchant for trickery. Which is more akin to the many folklore depiction of "Elves" that predate Tolkien's life by many hundreds of years, let alone his work on the LotR/Silmarillion novels.
Which is a big thing for Tolkien's races. They are not unique. None of his creations are completely invented by him. He was inspired by many past works, including folklore (As well as his own religious views, hence the subplot of the Valar mirroring the angels and Lucifer of Christian lore). Where he picked up on one of many depictions of these races to use in his works. There is still many other depcitions of these races that existed before him that can be used as inspiration in the future. As well as many different interpretations made after him which can also be used as inspiration (Which has had an effect, for example, "Green Skinned Orcs" is not from Tolkien who's Orcs are brown/grey/black skinned - Green Orcs comes from places like Warhammer, Warcraft and Elder Scrolls and have become the modern staple in lieu of Tolkien's version)
Hence why these races get not only used, but also readapted. They're popular races from folklore. So they are what people tend to think about when creating fantasy stories. It's not that they're creating new LotR media set in Middle Earth, they're just using a generic fantasy race and then using a different take on them than Tolkien took.
Sure, sometimes creators come up with new names for more unique versions of the same idea (For example, Warhammer has Eldar and FFXIV has Elezen instead of "Elves") but it's not a requirement and is really only to add flavour to their universe (Which FFXIV does a lot of, including things like having "Popotos" instead of "Potatoes" functionally identical and close enough that they're recognizable but is something unique that adds a bit of flavour)
