I've become okay with Species.
I liked heritage, but species has grown on me, as I think they were betting.
I do want a full separation of "genetic" and "learned" traits, though. The Playtests haven't thrown all the learned traits into the more robust Background system, and they should. If it's something that's iconic for that species, make a suggested backgrounds list or a section in the backgrounds chapter on species-iconic backgrounds (Elven Knight, Elven Sage, Dwarven Crafter, Haflling Wanderer, Halfling Farmer, etc) and note that you might be a Dwarf who grew up amongst Elves, and might take a look at the species-iconic backgrounds for Elves instead. And of course, none of these backgrounds are specific, just iconic choices!
I DO think the BG3 data would suggest they can't just relegate Half-Elf to a sidebar (while Half-Orc can very neatly be included as a paragraph within Orcs; already most campaign settings loop the two together when they talk about societies or how they're different in this setting).
To me, the Half-elf has NEVER felt like an Elf+ or a Human+, it's always felt like its own thing. Even if its new abilities are from the Custom Lineage mechanic, I would like it to have its own description page, and use it as the PRIME example of Custom Lineage, showing some classic choices for a Half-elf lineage.
This would require importing that custom lineage toolset from Tasha's, rather than just saying "you're an elf, but described as half-elf, and qualify as both species for the rare mechanics with a species' restriction).
