It's well written and the world feels truly alien. There's a lot of freedom in what you're capable of if you put your mind to it. Like you can cast spells that will let you jump across the entire map in one go. You can levitate over mountains. You can enchant a pair of daedric gauntlets that have a single fireball charge that will engulf an entire town. The world is full of mysteries and NPCs. The guilds feel more fleshed out, because they actually are in conflict with one another. For instance, a thieves guild mission could lock you out of another guild entirely. Joining one of the three great houses will lock you out of the other two. There's a much greater variety in equipment. Quests can have a lot more text, because every line doesn't have to be voiced. There's wild stuff like literal Gods roaming around some of the cities.

It just feels more fully realized for me.

I'm sure it's hard to pick it up for the first time these days, because the combat is odd. It's first person, but every attack is also still a dice roll under the hood. Just because you were close and your cursor was on an enemy doesn't mean they'll be hit. I think that's the primary thing that will turn off newcomers. Sorry about the rambling post, I'm not great at describing why I enjoy something and I also fully acknowledge there's an element of nostalgia with me and Morrowind.