But an elf can be everything a character can be without compromising on the fact that they are an elf. In order to play a Khoravar, I now have to decide whether they are the "human" kind of Khoravar or the "elf" kind of Khoravar, and for every future interaction with the game system, that is all that matters.
In Eberron, Khoravar is explicitly a native culture of some Human-Elves. Other Human-Elves have nothing to do with this culture. As a culture, the background is the proper design space to explore it. Having a background from Khoravar is precisely what defines a character as a citizen of Khoravar. Whether stats happen to start from Elf or Human is less relevant.
As far as I can tell, the Human-Elf matters, but not the Human-Orc. Players are happy enough to have the full Orc replace the old school Half-Orc.
(Actually in Forgotten Realms, Neverwinter seems founded by both Elf and Human, implying the multispecies is prominent.)
And if they actually do so, I will happily concede the matter.
But at present, everything they've said on the topic of mixed-ancestry characters is that they're not prominent/important enough to be worth consideration by the game system.
Except nowhere do they actually SAY that. What they say is "this character is a drow". They at no point acknowledge even the possibility that the character has any human heritage whatsoever.
The same UA that describes the 2024 species, also describes the multispecies.
It is true the UA makes it a sidebar. The 2024 needs to give the Human-Elf as an example of how to build a multispecies character. DnDBeyond stats show the Human-Elf continues to enjoy enormous popularity, and the recent Baldurs Gate does too. The 2024 Players Handbook does well to have a section featuring the Human-Elf.
Here is the UA verbage for multispecies.
"
CHILDREN OF DIFFERENT HUMANOID KINDS
Thanks to the magical workings of the multiverse, Humanoids of different kinds sometimes have children together. For example, folk who have a human parent and an orc or an elf parent are particularly common. Many other combinations are possible.
If you’d like to play the child of such a wondrous pairing, choose two Race options that are Humanoid to represent your parents. Then determine which of those Race options provides your game traits: Size, Speed, and special traits.
You can then mix and match visual characteristics − color, ear shape, and the like − of the two options. For example, if your character has a halfling and a gnome parent, you might choose Halfling for your game traits and then decide that your character has the pointed ears that are characteristic of a gnome.
Finally, determine the average of the two options’ Life Span traits to figure out how long your character might live. For example, a child of a halfling and a gnome has an average life span of 288 years.
"
For me, this approach to mixing any two player species works great. Hopefully the free background feat can help round it out. In addition, maybe the DMs Guide can suggest how to mix-and-match traits, requiring DMs approval.