It's interesting to me that occasionally this discussion refers back to the Tolkien-derived races, when even in his own works we can see that elves, dwarves, and orcs all have, or are implied to have, different cultures. This is very much a D&D problem.
Elves:
- Among the Eldar/High Elves, the Vanyar, Ñoldor, and Lindar/Teleri all look different (blond vs black/red hair vs silver hair) and have completely different cultures (Contemplative vs Forge & Sword vs Singer-Sailors) even while being Elves of Light and speaking the same language (Quenya) and living in Valinor nearby each other.
- Among the Sindar, who are also Eldar/High Elves but not Elves of Light, the cultures of the Doriathrim, Mithrim, and Falathrim are completely different, despite sharing a language (Sindarin) and historical background (Teleri/Lindar who remained in Beleriand rather than travelling across the sea to Valinor). They all look somewhat similar as they were originally Teleri, but their nation-states are quite different.
- The Dark Elves or Avari are split into at least 6 different tribes that broke off of the Teleri and Ñoldor during or before the journey west because they didn't believe it was a good idea to travel to Valinor. Some got corrupted into Orcs, others remained in the wilderness, others travelled west later and were either good or not. We know little about their cultures, save for Eöl the Dark Elf.
- The Nandor or Wood Elves or Green Elves or Laiquendi or Laegrim or Silvan Elves are another group of Teleri and/or Avari and or mixed group that broke off and decided to live in the woods. There are dozens of these tribes that are similar but also different. the Laegrim or Laiquendi of Ossiriand may be different from the Silvan Elves in Mirkwood and Lothlórien, even if they shared an origin.
- In the 2nd and 3rd Ages, many of the great Elf kingdoms are gone, and there's a consolidation of Sindar and Ñoldor in Middle-earth since the elves have mostly travelled west to Valinor by now, but the remaining kingdoms are all very different from each other, despite being made of of mixes of different types of elves:
-- Lindon is made up of former Falathrim, Ñoldorin, and Laegrim, and in the 3rd Age culturally serves as a neutral role among the realms of Elves given that they are the main exit from Middle-earth for the departing Elves. And yet, for the 2nd Age, they were avoided by other Silvan elves leaving because of old conflicts with the Ñoldor. Hence why King Amroth of Lórien tried to leave Middle-earth from the south in Gondor, and ended up dying there at Dol Amroth (and his beloved Nimrodel's handmaiden married into the Gondorian humans there creating another half-elven community).
-- Imladris or Rivendell is the house of the Half-elf Elrond, whose ancestors include his grandparents Tuor (Hadorian Human), Idril (Ñoldorin High Elf), their son Eärendil the half-elf (so, daddy is Half-Ñoldorin High Elf), Beren (a Bëorian Human) and his wife Lúthien (Half-Doriathrim Sindarin High Elf, Half-Angel, possibly better statted as an Aasimar given this), their son Dior (1/2 Human, 1/4 Doriathrim Sindar High Elf, 1/4 Angel), his wife Nimloth (for all intents and purposes a Doriathrim Sindarin High Elf), and their daughter Elwing - Elrond's mother - who is thus 1/4 Bëorian Human, 1/8 Angel, and 5/8 Doriathrim Sindarin High Elf. This makes Elrond, wait for it, 1/4 (4/16) Ñoldorin High Elf, 1/4 (4/16) Hadorian Human, 1/8 (2/16) Bëorian Human, 1/16 Angel, and 5/16 Doriathrim Sindarin High Elf. Or all in all, 9/16 High Elf and 6/16 Human and 1/16 Angel, so Elrond could be statted as an Aasimar if you think the Angel drop of lineage is more important, but for the narrative he's a Half-elf because he's just barely more Elf than anything else. Given all this, Rivendell is a place that welcomes Ñoldorin High Elves, Sindarin High Elves, and their Laegrim Wood Elf kin (as Beren and Lúthien had lived amongst the Laegrim for a long time), as well as Human Númenorean Rangers and men of Gondor, as they are descended from the Houses of Bëor and Hador, and Angelic wizards like Gandalf and Saruman. It's a melting pot that welcomes pretty much everyone to stay in this house and is a main reason it's where the White Council and Council of Elrond met, and why Thorin's Company was welcome there and not in other Elven realms.
-- Speaking of, Thranduil's Woodland Realm in Mirkwood is mostly Wood Elves with an upper class leadership of Sindarin High Elves. And Thranduil built his realm in the manner of Doriath and Nargothrond given that he had lived in Doriath as kin to the King there. They're extremely xenophobic against the Dwarves but very friendly to their trading partners, the Lake-men, and are overall less wise and more cruel than Elrond's people. But Legolas comes from them, and he's not bad at all. They're not evil, but it's a very different culture from elsewhere, and these cultural clashes with Durin's Folk nearly causes all-out war between the Elves and Dwarves in the Battle of Five Armies.
-- Further south, while King Amroth and his father Amrod ruled Lórien for a long time, they are Sindarin High Elves while the people are mostly Wood Elves. Later, after the fall of Eregion, Galdriel and Celeborn came into Lórien and were welcomed, turning it into a forest of lights, and creating a melting pot of Ñoldorin High Elves that came with her, Sindarin High Elves that came with her husband, and the preexisting Sindarin High Elves and Nandorin Wood Elves that had lived there previously. And all of these elves then branded themselves as the Galadhrim - the People of the Giant Trees and/or the People who Serve Galadriel - because their culture was more important than whether they were Wood Elves or Grey Elves or Deep Elves.
-- Eregion itself, back in the 2nd Age, was almost ENTIRELY Ñoldorin, being the home of Celebrimbor the smith-son of Fëanor jewel-maker. Celebrimbor made the Rings of Power, and Galadriel was complicit there as she was with the kinslaying of the Teleri when she left Valinor. So she and Celeborn lived in Eregion for a while as well, and left when Sauron revealed himself to the 3 Elven Ringbearers as having deceived them. Despite the old animosities between the Ñoldorin of Nargothrond and the Dwarves of Belegost and Nogrod (over the issue of the Nauglamír necklace that included the Silmaril of Beren and Lúthien that is now the Eärendil morningstar/eveningstar in the sky), the Ñoldorin of Eregion and the Dwarves of Moria/Khazad-dûm were friends, and Celebrimbor wrote in Elven runes Cirth Ithil (Moon-runes) upon the west gate of Moria - speak friend and enter. Much of the wealth of Eregion and their great and lesser rings' jewels and metals likely came from the wealth flowing from Moria's mithril and the House of Durin's other holdings in Erebor and the Iron Hills, where gold and silver and jewels were more readily mined. But the Elves of Eregion would not have been friends with the Dwarves of the Blue Mountains, who are likely the descendants of the Dwarves of Nogrod and Belegost back in the 1st Age who had such major beefs with the Elves.
See where I'm going with all this?
That's just the Elven realms we know about in Middle-earth. There's essentially 3 subraces of Elves in Tolkien: High Elf (Vanyar, Ñoldor, Lindar, and Sindar), Wood Elf (Nandor, Laegrim, Silvan Elves), and Dark Elf (Avari). But the cultures and kingdoms all had their own alliances, their own architectural styles, their own mindsets, their own approaches to categorizing the elven peoples, even. I barely touched on the different cultures of the Ñoldorin kingdoms in Beleriand, but lets just say that Finrod's Nargothrond, Turgon's Gondolin, and Maedhros' Himring had VERY different approaches to the rest of Elvendom let along other free peoples, despite all being close kindred.
Then think of Eöl the Dark Elf, and his half-dark elf, half-Ñoldorin son Maeglin, who betrayed Gondolin to its ruin out of his lust for his cousin Idril Turgon's-daughter (who as you may recall from above, was already married to a Human of all people, Tuor, who had essentially been made an honorary Elf and for all intents and purposes is believed to be chilling in Valinor with Idril and the gods as if he were an elf because of his elfiness and service to the Sea Archangel Ulmo/Poseidon/Njördr/Varuna/Nuada).
This is what we need out of D&D.
We don't need this level of world building in the player's handbook. But we need PC lineage attributes that don't hamstring the player into thinking that all Wood Elves are like Legolas (who isn't even a Wood Elf, lol) or all High Elves like Galadriel and Celeborn. And not all Dark elves are like Eöl and Maeglin. A bunch are just integrated into Wood Elf communities, or doing their own thing, and yes, others are evil or even have been twisted into Orcs. Maybe. MAYYYYYBE.
We don't need the assumptions to be stereotypes. We do need exciting ideas to jump off with for characterization for players and DMs.