I've been thinking the same recently. Booted up Morrowind on my tablet recently and revisited Oblivion and Skyrim. The character development is so lacking in Oblivion and Skyrim, where it isn't in ESO or Morrowind for very different reasons. In fact, I respectfully disagree with the poster above who said that ESO's world building and lore is its strong suit and Oblivion/Skyrim's storytelling is it's strong suit. I feel the opposite way actually.

ESO has the luxury of visually depicting all of Tamriel Whereas Skyrim and Oblivion can take a laser focus on that part of the world. The writers at ESO have therefore written in characters and story arcs to make the world seem "lived in" without stepping on the toes of the lore building required of the main games. Meanwhile, Oblivion and Skyrim can feel kind of soulless at times, with one-dimensional characters and narratives. But Skyrim/Oblivion have this rich cultural world building that compliments the higher attention to detail and scale they're afforded.