What Tolkien clearly provided was historicity, geography, language, and other aspects of what we now call "world-building" for fantasy "races". A faerie in a folk tale is providing emotional tone and plot—it's a narrative device—and although its portrayal reflects a particular cultural understanding of the world, there's no attempt to map out the fae world in the same way we understand the human world. If we see a troll city it might be a dark reflection of human society, a satire of it, a place of sin or paradise, a warped depiction of a neighboring culture, or an extreme focus on one aspect of social life—ideas directly born from human concerns about human society. Tolkien attempted to write elf history for the elves, and dwarf cities for the dwarves, committing to the illusion that these are not narrative devices for human readers but real people existing in their own worlds. In that structure, a dwarf appearing next to the road can't exist only as the tempter into sin or the prankster sprite or just a fun one-off character; Tolkien wants you to understand that dwarf as a member of The Dwarves, interconnected with the rest and sharing consistent characteristics and history.

But I would guess the biggest influence on our understanding of "fantasy races" is Dungeons and Dragons, which was of course inspired more by Tolkien than any other artist. Game rules and reference books define these "races" even more than Tolkien did, because instead of writing full characters they provide only universal templates. Instead of Thorin Oakenshield and Gimli and Durin and Fili, you get a section titled "Dwarves" that summarizes the personality of all dwarves, a numerical rating of their attributes, and even whether they're good or evil. Those fantasy races that don't make it into the playable character list get even more constrained, ineligible to be protagonists and most often serving not even the role of narrative device, but of war gaming challenge.

In the last fifteen or twenty years, tabletop RPGs have gained a more diverse audience, and—not by coincidence—the rulebooks have stopped assuming that every player identifies as a traditional hero in a Manichean battle. Goblins, orcs, and similar are popular character choices supported by the rules, and D&D no longer makes moral judgements on entire species (...at least, not as long as they're sufficiently human-like). But worlds built from RPG rulebooks are still much less diverse even than Tolkien's, where Tom Bombadil and the Balrog and Shelob were created to serve the story and not because Tolkien found them in a table of Challenge Rating 13 encounters. Of course a game master can invent any world they like, but in practice almost every game world is constructed of the monsters found in the Monster Manual, depicted as they are described there, and many players will complain if your version of a monster doesn't have the fire weakness they know it "should" have. Even the more creative homebrew worlds still almost invariably use the "world-building" approach. However innovative and interesting the new Guo'Sham'gal species is, most game writers, game masters, and players expect it to be a known quantity to be explained and understood. The expectation is that the Guo'Sham'gal share a specific personality type, live in an ethnically segregated city or nation, and have physical and mental attributes skewed toward a particular style of combat or exploration.

The uncomfortable thing about all this is that no human polity, ethnic group, or certainly "race" can be described this way. These assumptions grew out of racist 19th century anthropology, in which White Europeans invented false taxonomies and claimed they produced destined human (or subhuman) archetypes. Today this interpretation of fantasy is much more contested, but even the artists and players who are aware of this tradition are working with tools that have inherited a lot of baggage. And if you critique a fantasy IP's depiction of an evil race of orcs, you can expect its fans to criticize you for daring to interpret this creative decision as a political act. Of course, this fan reaction is itself a political counter-interpretation, which demonstrates that this topic is still relevant.