Honestly the Fey/Celestial Eladrin issue was basically solved by the DMG, Elves born in Arvandar are born Celestials.
No I think the strange twists in this lore are caused by the amazing diversity of elves in general.
Wild Elves, Wood Elves, High Elves (Sun/Moon/Stars races within High Elves), Averial Elves, Sea Elves, Artic Elves, Desert Elves, Sea Elves, Dragonlance's version of Sea Elves, Lythari Elves, Drow, Fey'ri, Eldarin, Shadow Elves, and now Shadar Kai Elves. Plus Half Elf versions of all these Elves.
All of them are very very different from each other on a physical and mystical level.
Now compare that to Dwarves, Hill and Mountain Dwarves have somewhat different skin colours, a bit different cultures, but less different then many human cultures are from each other.
The same is true for Gnomes subraces and Halflings subraces, compared to Elven subraces they are basically just different cultures with minor physical differences.
The exception being Duegar, Deep Gnomes, and Ghostwise Halflings, but there is reasons for those odd exceptions. Duergar where experimented upon by Illithids, Deep Gnomes I'm not sure why caused Deep Gnomes, and Ghostwise Halflings only a single magical ability, telepathy.
No I think the strange twists in this lore are caused by the amazing diversity of elves in general.
Wild Elves, Wood Elves, High Elves (Sun/Moon/Stars races within High Elves), Averial Elves, Sea Elves, Artic Elves, Desert Elves, Sea Elves, Dragonlance's version of Sea Elves, Lythari Elves, Drow, Fey'ri, Eldarin, Shadow Elves, and now Shadar Kai Elves. Plus Half Elf versions of all these Elves.
All of them are very very different from each other on a physical and mystical level.
Now compare that to Dwarves, Hill and Mountain Dwarves have somewhat different skin colours, a bit different cultures, but less different then many human cultures are from each other.
The same is true for Gnomes subraces and Halflings subraces, compared to Elven subraces they are basically just different cultures with minor physical differences.
The exception being Duegar, Deep Gnomes, and Ghostwise Halflings, but there is reasons for those odd exceptions. Duergar where experimented upon by Illithids, Deep Gnomes I'm not sure why caused Deep Gnomes, and Ghostwise Halflings only a single magical ability, telepathy.