Again, considering that the only difference between a 2014 half elf and a 2024 half elf is a couple of proficiencies, i'm really, really not seeing the problem. Don't want half-elves to trance? Ok, drop the ability. A tiny bit of flexibility on the part of the individual table resolves 99% of the issues.
This isn't just about Khoravar - it has never been just about Khoravar. If I want to play a dwarf-dragonborn, I want the ability to mix their species traits. If I want to play an elf-tiefling, I want the ability to mix their species traits. If I want to play an aarakocra-tabaxi, I want the ability to mix their species traits.
You have made it abundantly clear that you don't find "half-elf" species traits to be interesting enough to care about, but this affects every possible mixed ancestry species permutation, especially including the new ones they are supposedly looking to add into the game. The only reason I bring up Khoravar as a specific example is because they have an established history in a setting that I happen to care about - namely Eberron, making up a major population block in Khorvaire and two of the Dragonmarked Houses (with "half-orcs" making up a third).
If they truly want to expand mixed ancestry representation, I feel a mechanical toolset is needed. Without it, this entire effort feels like saying "We're uncomfortable talking about half-elves and half-orcs, so we're shoving them into a sidebar, saying 'you can play any mixed ancestry you can imagine', and otherwise erasing all mention of them."
I'm admittedly a little worried that it's going to result in them scrubbing them out of settings that actually use them in interesting ways - it's not as prolific with "half-elves", but I've heard plenty of talk from people saying there's no point in having "half-orcs" anymore now that full orcs are an official PC option, because "all half-orcs ever were was a sneaky way to play an orc when orcs weren't allowed". I don't want Eberron to lose Khoravar and Jhorgun'taal. I don't want House Tharashk to become full-blooded orcs, House Medani to become tieflings, and House Lyrandar to become goliaths. But because so many people seem to be coming at this from a FR-style mentality of "half-elves/half-orcs have no society of their own, they only exist on the periphery of those of their parent(s)" and see them not as a "people" but just an assortment of singular individuals that can be easily and painlessly discarded, that's the direction this feels like it's going to me.
The entire discussion surrounding this (in general, not specifically with you) has consistently sounded to me less like a legitimate push to allow for more diverse mixed ancestry representation and more like a way to quietly sweep them under the rug by making the option available, but completely irrelevant and largely invisible.
And that's a problem how?
For the same reason we don't force people to use up their Background to justify playing an elf or a human. It's putting a mechanical tax on the right to play a mixed ancestry character that no single ancestry character has to pay, and consequentially creates a disincentive for playing mixed ancestry characters.