I'm sorry to see the Ardling go -- I thought it was great.
* It broke free from the Tolkien/Eurocentric mythos, and gave a generalize theriomorphic species that could be mapped onto Egyptian/Iranian/Turkish/Chinese myth, as well as tapping into a number of fantasy worlds.
* The Animal Ancestry gave a choice of 4 movement-related bonuses (three had a small combat bump). One of them -- the Flyer -- gave us a 3.5 version of Feather Fall, which only affects the "caster". It was good, balanced design, giving wide range within a single umbrella.
* The choice of a cantrip is a minor boon used elsewhere. I would have preferred it from the Primal list rather than the Divine list, and for the species to be tied to this plane, rather than Celestial. (It also had proficiency in Perception, which I think should go from all the species that have it - elves, etc.
* It was a simple design, much cleaner than most of the racial designs with fewer bells and whistles, but flexible and would have been a great substitution for the Custom Lineage in Tasha's.
I'm more sad about the Ardling just because of how it may affect WotC adding the other planetouched/planar races. Who doesn't want Bariaur, Rogue Modrons, Axani, Cansin, Chaonds, Mechanatrixes, Shyfts, or Zenythris showing up at their tables?
I think they just should have started with Aasimar instead of making the Aardlings, and then they really muddied up the concept of the Aardling with the animal thing. Now while they strongly connected the Aasimar with Angels, I felt that was a mistake too. They should have just had 3 celestial legacies of standard 3 spells for a core PHB Aasimar that are counterparts to the 3 common Tiefling legacies, and then said that there are rarer legacies of Aasimar (the ones in Monsters of the Multiverse) out there.