It's a matter of perspective, but the only possibilities are that they are too alien to play, or they aren't.
If they're human enough to be playable, then that falls into rubber-forehead territory. Maybe. YMMV, but the poster boy for Rubber-Forehead Aliens is Worf, who is constantly going on about honor and duty, and having his weird biology play a role in the plot. In order for a race to be different enough to not just be some extreme sort of human, it would likely be alien enough that it wouldn't be easily playable by a human.
There
is a middle ground. Take elves, for example. Assume that they aren't wholly alien, rather the closest to human the fey can get (or vice versa). They're human enough to be comprehensible, but alien enough to warrant a separate race.
They have insanely long lives (I still use the 1E 1500-2000 years for my home brew), don't really sleep, aren't particularly sturdy, but innately imbued with some magical talent. The also have a spirit, rather than a soul, and know that death holds reincarnation, rather than an afterlife -- this is the nature of the Reverie; they have visions of past lives and relive elements of them.
Between the long life and the Reverie, elves have an essentially timeless outlook. Sure, they lose muscle memory and some of the details of crafts and skills, but this can be seen as an opportunity to learn something new or even re-experience the joy of learning something extraordinary for the first time. It also means that elves have little fear of dying. That's not to say they're suicidal, but they
know what awaits them and have been through it before -- their outlook on death would be much like a Christian martyr, both with the added weight of experience and tempered by a rebirth into the same world rather than a better one.
The long life of elves, relative to others, gives them a perspective on life as well as death. Humans have the comparable lifespan of a Guinea pig. Even a dwarf would be like a dog's lifespan. Clearly, these races are of comparable intelligence, so they wouldn't be viewed as pets. But interacting with humans would always be like meeting someone shortly after they'd been diagnosed with terminal, incurable cancer. Even in the best of cases, they'll make a number of decisions based on their impending demise. Can you keep up with the frantic pace of rushing from one deed to another, never savoring the victory, but always looking for the next thing to complete before it's too late? How deep of a bond would you be willing to forge with them, knowing that they'll wither and die by the time you're really getting invested? If you've ever dealt with aging relatives, you know what it's like to not know whether they'll still be there for your next visit or if this is it. That's every parting between an elf and a human.
That same perspective makes elves abhor unnecessary killing. Why destroy something that is so fleeting? Even the most annoying orc will die in a short span. Sometimes you have to put down a mad dog -- and orcs have more than their fair share of those -- but it isn't something to be reveled in.
Now, a significant amount of that is cultural -- or is it? If you took a colony of human babies and somehow raised them without cultural interference, I'd wager that you'd see some very similar patterns within a couple generations, just from biologic sex drive. A good amount of the alien nature of elves comes from their lifespan, which can't be escaped. Sure, you can have an elf who
does view humans, etc. as pets, just because of their short life, but it's still a factor. If you want to twist the elven stereotype (which I very much approve of), you should still be asking how the uniquely elven traits shape you in ways that human isn't.
I won't speak for Celebrim, but I, personally, prefer a human-centric game because I find most people don't really think about how those alien traits would shape their characters' behavior. An elf is often different from a human only because they have stat modifiers and darkvision and maybe they're just a little sexier. If that's all the non-humans are, then I don't really want to bother. Just make a list of "racial" abilities that can be taken instead of the feat for the variant human. The old literary adage is that "if it doesn't add something of value, don't include it". I'd apply this to D&D races, too. BTW, this is why I don't generally use halflings; they're just short humans and don't really have anything "alien" to set them apart.
FWIW, most of my "this is an elf", above, comes from "The Elven Point of View" in Dragon #60, which was reprinted in "Best of Dragon Vol. III". Once again, I'll put in my plug that Dragon and Dungeon should be revived because they create durable value, even 30 years later.