Bodies, sure. I'm talking about their minds, though. Scientists are fairly sure that humans are as intellectually advanced as we are, in significant part, because of how long we take for our brains to finish cooking.
I guess the difference for me is, I think it's plausible for a human to be walking within hours of birth and talking within the first few months, and once you're at that point, the two species develop at very nearly the same rate, dragonborn being very slightly faster.
That is: dragonborn children start off with about the development of a 1-year-old human at hatching. (As mentioned, I think part of this comes from exposure to the world prior to hatching, allowing the child to begin brain development earlier than humans, though that could be unrelated fluff from a different game leaking in.) By the age of 1, they are as developed as a human child of age 3. By age 12, they have finished growing to adult height and simply need to gain muscle mass and refine their existing development to be fully mature, which occurs at about age 15. In humans, adult height is usually reached at age 15-16, depending on the child's sex, genetics, etc. and most brain development and full sexual maturity is finished somewhere between 18 and 21.
So dragonborn start with about a 1-year head start, it advances to a 2-year edge by (their) age 1, and becomes a roughly 3-4 year edge by age 12, possibly rising to as much as 6 years by age 15, possibly falling back to only 3 years. So if we were to plot human-equivalent age vs dragonborn-equivalent age, we would get (0,1 (1,3), (12,15.5), and (15,19) using more or less "average" numbers on the human side. With those numbers, dragonborn on average mature about 17% (slightly over one-sixth) faster than humans, and have a head start of a little less than 16 months (from a linear regression model.) If we use slightly more generous values for the latter two data points, I can get it as high as 28% faster average development (though the head start remains about the same, a bit over 15 months.) So we can comfortably say dragonborn have incredibly fast infant development coupled with a major head start, but after that, they seem to level off much closer to human maturation rates. (Since, unless you use the more generous numbers, dragonborn finish puberty about 3 years early and reach adulthood about 3-4 years early.) So the question becomes, is it plausible for a creature to have fully human-equivalent faculty development if their "infancy" gets essentially a full year head start and proceeds at about twice the speed of human infancy, and then settles into more or less the same development speed as humans thereafter?
I am of course not a pediatrician, evolutionary biologist, neurologist, nor childhood development psychologist, nor indeed any variety of biologist, psychologist, or doctor. And I carry plenty of personal bias here, as I developed some skills very quickly as a child, so I have weird personal ideas about when children can pick up various skills. (My parents love to tell embarrassing stories about people being impressed by my ability to speak full sentences at about 3 years old...unfortunately tending to be tactless and not very kind, because at that age I didn't understand that truth alone is no excuse, you must also be respectful and kind in your use of it.) My word is about as far as you can get from solid, reliable biological analysis of human development.
But I gave examples of human prodigies for a reason. Alexander the Great stands out amongst human commanders for good reason, and one of those reasons was his youth. His capacities developed shockingly quickly. Mozart, likewise, was composing his own music (with his father as transcriber) at age 5, at which point he had already learned to play the clavier (apparently extremely well), and wrote his first (short) symphony at age 8. These are of course extreme cases, the Dougie Howsers of the real world, but they point to the notion that it is at least possible for humans to develop at shocking paces and still be...well, human. Dragonborn just do so consistently, rather than as a rare fluke.
But that even moreso reinforces the issues I mentioned earlier. Dragonborn are going to be incredibly sensitive to inadequate nutrition (given they're pushing the envelope for sapient development rates.) They trade the risks of female injury or illness during pregnancy or after birth for the need to zealously guard and maintain hatching grounds for their children, and because of their faster generational turnover, they'll need to secure greater food supplies faster than humans do in order to keep up. Their relatively increased manpower mitigates some of these concerns, but doesn't erase them. With early childhood being so fast, there's no margin for error; a serious illness or injury in early childhood is probably a far more harmful thing for them than it would be for humans. This will have a host of implications (dragonborn are almost certainly
fiercely protective of their children in the first year or two of life; they will almost certainly prioritize childhood nutrition above all else; wet nursing is likely to be seen as a particularly pro-social/valorous thing; etc.) But it doesn't seem totally implausible. Fantastical, to be sure, but much more within the realm of physical possibility than bus-sized flying sneks that have truly biblical halitosis.
And I'd say that dragonborn and humans have a much greater difference than wolves and coyotes.
I wasn't trying to imply they were. Just giving an example of really different development rates in species. I chose them for their similarities only to avoid a rebuttal of the form "well of course wolves and bears mature at different rates, they're totally unrelated!" Which you can bet your bottom dollar would have happened if I'd used something like wolves vs humans.
"Elves aren't mired to the past!"
writes about how Elves are mired to the past like Elrond thinking of all humans as corrupt like Isildur
"Elves aren't stagnant!"
Elven Society is presented as unchanging and ethereal across practically every setting
"Elves use what they take from the past to shape their future!"
Thranduil refuses to help the Dwarves fight Smaug but gets ready to kick 4 other armies butts in order to take their stuff even though the stuff he wants from the dwarves is stuff they made or stole or whatever from other elves showing that they're capable of holding onto it and also just killed a dragon that he wasn't sure his people could defeat
"Elves aren't against change, they just know the world will change itself without their interference!"
Every Half-Elf's parents had a torrid hidden romance 'cause the elders wouldn't approve of them mingling with other races, often characterized as 'lowering' themselves or being 'doomed' by their love in a setting-reinforcing magical manner
The writers -say- they're not these things, but then make them exactly these things. In various stories of the Forgotten Realms or Greyhawk or Dragonlance it is the actions of Humans and Half-Elves and Hobbits and Dwarves that shake things up because the Elves act in a largely stagnant matter citing past battles and situations as the reason for their continued stagnation and refusal to do things that might upset the status quo, even when the status quo is horrible.
It does seem to me that you're leaning rather hard on just Tolkien and Dragonlance. While these are absolutely huge, they aren't the only show in town, and "elf" in D&D doesn't have quite the same impact for a variety of reasons. Probably the biggest is that D&D elves are not functionally immortal. They live much longer than humans (700 years IIRC, so about 8-10 times longer than humans), barring illness or injury, but they aren't immortal and that makes a pretty big impact.
In my own setting, elves live to be about two hundred (roughly the same for dwarves), though about the final 30-40 years of that is being "elderly," when most of them will want to retreat from everyday life. As a result, some elves are in positions of wealth and authority, but not all. This is a semi-mercantilist economic situation, not truly capitalist but with some such leanings, taking heavy inspiration from the Seven Voyages of Sinbad the Sailor. Some of the merchant-prince types are like Carnegie, using their wealth to improve the city, while others are metaphorical dragons sleeping on their beds of gold and jewels.
(In once case, it's a literal dragon! But that's a secret, the dragon masquerades as the new scion of each generation of a "family" of merchants.) Humans may not have the same lifespan, but generational wealth is generational wealth regardless of how it was obtained, and there are other advantages to having a changing face more often. Elves are also mostly native to the temperate southern forests, and are thus a small minority in the Tarrakhuna region where the game is primarily set. Half-elves are actually more common than elves, since I go for the 4e-style approach there. Those elves who do live in the "elf" forests tend toward much more restrained, village-style living for cultural and religious reasons,* more similar to the Nomad Tribes of the Tarrakhuna than the city-folk who are the usual suspects for fat-cat merchants.
*Long story short: they are the remnants of the El'Adrin civilization, somehow altered by the event that the rest of their civilization fled from into a pocket dimension. They have long awaited the "return." Many areas of their forest cannot be permanently settled, as new buildings crumble at ridiculous rates; this is a "curse" meant to keep outsiders from colonizing the El'Adrin former holdings, so that they won't kill anyone when their cities re-integrate with the mortal world after the "return." What exactly they were escaping, why it would have ended their civilization (other than "because magic changed"), and what must be done so they can return, are all open questions we'll resolve as we work through our Battlemaster's personal story.
"Show, don't tell" is alive and well in media. And it shows us that Elves don't fit the blurbs and excerpts that get assigned to them.
"Show, don't tell" has its limits though, and I find "broad sweeping conceptions about an entire culture" are often hard or even impossible to demonstrate purely through showing. Mostly because showing is, by its very essence, about particulars: individual people, single buildings or marketplaces, a particular piece of music or local cuisine etc. Could one capture the incredible depth and variety (and beauty) of Hindu religious practice exclusively through showing individual believers? Maybe, but that's gonna be a huge amount of work, taking up a significant chunk of the story, and you're going to need like five different characters who all go into fairly deep detail about their practices. That's not really feasible.
"Show, don't tell" is important when a deep, dramatic, impactful moment is desired. Doing the reverse is in fact quite useful in many cases, where only the gist is necessary to keep the story moving forward and an in-depth "shown" depiction would weigh down the story with turgid prose.
