I think, and apologies for anyone whose sensibilities this offends, but fantasy races -and the games containing them- have no reason or obligation to "be the same/have the levels of diversity" of humans.
The "lumpy forehead humans" argument is only emphasized and exacerbated by saying "all demihumans have to have all the same skin tones and cultural differences as humans have [and, somehow, also MORE fantasical and bizarre variations of color and style]. You're actually making the species MORE just dull variations of humans with pointy ears.
What is really important here, is how the species are defined or created within the game setting. Were they made to just be mirrors of their surroundings? If so, then all the humans, elves, dwarves, halflings of an "tropical/jungle/African-inspired" analogue area would be darker skinned? Ok, fine, if that's what you want. Then the "northern/tundra/snowy/Scandanavian-Norse-Vikingish analogue realms are all fair-haired alabaster skinned warrior cultures? Sure. Why not.
Is that "inclusion" really making a fantastic magical world feel LESS "racial" motivated or narrow?
I mean, if that's how it things are in your world, then great. More fun for your table? More bettah. But don't pretend that somehow makes the game or any particular product, "more/better fantasy" or "improves D&D."
What if the Elves are the result of a blood splatter of star gods from a battle in the time before time? Timeless. Magical. Pure "divine essence" [Spirit] made Physical in form by direct mixture with the physical/natural world of Creation - but not "made" or shaped by- the source of their existence. Bringing magic to the world, by their very presence. Being simultaneously and spontaneously created and sustained by that same world, now infused with magic... that they are/caused.
Do they have blue or grey skin if they live in the mountains/attune to the sky and green (or brown, woodlike) skin if they live in the woods? Do they have every skin color that humans -not yet created/in existence in this world- have? Do they have skin tones in all colors imaginable?
Is it "not inclusive enough" to say elves who have -over centuries- migrated and attuned to the desert to be sandy or golden in complexion? Is that racist/racism? Is it more or less racist/racism if you "can't" play a "desert elf" with african-american skin tone? Or if ALL have african-american skin tones but you "can't" be caucasian or have celtic-colored eyes/hair [if you're a desert elf...or a mountain elf...or a swamp elf?]
Is it "not inclusive enough" to say these beings, magically, spontaneously, created by drops of godly blood are uniformly pale-skinned -even, legends say, sometimes luminous- with golden or silver hair, and sparkling vibrant eyes all the shades of the sky -day or night? That they, similarly, have a uniformity of form and shape, growing in a lithe fitness and toned musculature, making the differences in [what humans consider] male and female body types blurred -paying homage, if nothing else, to the longstanding descriptions of androgyny of the appearance of D&D elves? Is it "lumpy forehead" to say elves do not possess "souls" as humans (and some -not all- other species) but are, themselves, independent of spirit and can -but do not necessarily- carry on to "an afterlife," posthumously, as human mythos and religions claim human souls do.
Is that more "too samey" as humans or less?
Were the dwarves carved -deliberately - secretly - from the bones of the earth with the breath of life [the soul] placed within them by the Elder deity of stone and smithy to be his servants/helpers? Is it "inclusively appropriate" for them to be any human skintone? Or all the colors found in rocks and ores? OR a uniform dull "stone" grey? Or rich earthy brown? Loam or wrought iron black? Were they "made" to be diverse?
What if halflings are descended from the original Eight Clans of gnomes. Now calling themselves by various names in various regions, the "halflings" were merged with the Material plane. Unlike other clans that wandered to the realms of Faerie or Shadow, the Elemental Plane of Earth and other places, halflings "never left" the green fields and quiet dales of the world they were originally birthed from [by the ancient titans...or dragons?] to tend? What if they have long-forgotten their origins, to the point of any ancestry mixed with the gnomes is found laughable by all. That they have lost nearly all magical power/prowess they possessed in the age of dragons and titans. But they have mixed so much with other species through the eons, since their origin of species, they are found in all skin tones and facial features familiar to humans...but still all have hairy feet and a slight point to the ear. OR can they be found in all the colors of tubers/roots? Or are they a uniform "ruddy tan" from their hours (and love) of outdoor work, pastoral past times, love of drink, and "earthy" associations? Which is more fantastic? Which makes more sense based on the species' creation in the setting?
My point is, does inserting "racial diversity/inclusivity" -across the board, of all species- make sense to the world? Does its insertion improve the FANTASY... the internal consistency of a given setting? IF you find that it does...and it provides or improves the fun at your table, GREAT! Awesome. Have at it.
But, I truly do not think/see how a uniform proclamation of such, by the company as, somehow, made D&D "canon" in the game would/could be an overall benefit. A mention/nod/sidebar that it is completely possible for any table/setting. Sure. But not - IF the goal is to make semi-humans feel and play LESS "funny/different shaped humans" - as a matter of course.