I am surprised that it is the Gnome that is the OP has trouble with.
To me, it seems like it is the Halfling that is lacking any identity. Sure, Gnomes have a somewhat confused identity split between being techies and hippies, but at least there is something to say about them.
But Halflings? Basically just humans who don't grow to full height. You go back to Tolkien and it seems like they were stand-ins for the simple, rural country folk of the British Isles-- and he made them small in stature as well as in status. But in D&D, such people are just common humans-- and anything else that has attempted to slip into the Halfling identity has pretty much fallen flat. All their racial traits and such are simply based on the idea of "a human, but smaller-- so what might someone be able to do if they were smaller?" But it isn't as if the Halflings have a monopoly on being small size and thus get racial abilities that seem like they should just be general rules of the game such as "you can hide behind a creature twice as big as you" or "you can run between the legs of something twice as tall as you"
None of that speaks to anything particularly unique or iconic or interesting for them. So while the Gnome identities might contain some level of contradiction, at least there are some iconic Gnomish traits and concepts to play with. Even if it boils down to being scientists, talking to animals, using illusions and wearing pointy hats. It is a lot more than what the Halfling has going on.
But, that aside, sure... there gets to be a point where one needs to ask "do I really have to have everything in my game?"
Do I have to have Aasimar, Tieflings, Aarakocra, Goliath, Dragonborn, Genasi, Kenku, Grung, Bullywogs, Tabaxi, Triton, Gith, Shifter, Warforged, Kender, Minotaurs, Changelings, Firbolgs, Eladrin, Deva, Shardmind, Kalashtir, Thri-kreen, Hamadryad, Pixie, Satyr, Revenant, Shadar-Kai, Shade, Vryloka, Bladelings, Hengeyokai, Jerren, Vasharan, Korobokuru, Nezumi, Spirit Folk, Vanara, Synad, Illuman, Mongrelfolk, Sharakim, Centaur, Raptorian, Killoren, etc., etc.
Apparently everything that anyone has ever thought up and stuffed into any published D&D book needs to be a common, recognized, regular sight and occurrence within every world that the system is ever used to represent?
Honestly-- that just seems crazy. A world is going to be as much defined by what is not there by what is.
That being said, I am a big advocate of what D&D has thus far completely failed to do.
If there is a sentient, true-breeding race that generally pops up as villains within the setting and that race has lived in that setting for more than 100 years, then there should be a properly made, properly balanced racial stat block for playing that usually villainous race. And, no, not "Half-"-- just an outcast or exile or traitor or imprisoned and reformed or adopted and raised member of that raise.
And, no, giving them intentionally crap stat block that puts them half a level to an entire level behind the rest of the entire party does not count as a "properly made, properly balanced" racial stat block. Nor does making them a few traits short and then making up for that by giving them a super broken ability that violated the core design principles of the game.
