I would still like to hear the affirmative case for the ardling at all, but especially in the PHB. It feels very much like a designer's pet idea in search of an audience, rather than a response to audience demand.
There's a ton of popular races out there, and with D&D Beyond, WotC can actually get a feel for what people want. Unless I misremember, both goblins and kobolds (despite sometimes lackluster stats) are wildly more popular than any animalian race, for instance.
Eldritch Blast being a class feature is good design. If it's a must-have for 99% of builds, making it a choice just exists as a trap choice for new players and a customization choice for the unicorns who want to do something different. If they want to provide a build that doesn't use Eldritch Blast, put that into the subclass features.