Why isn't there a direct landroute between these two major cities? You can see Sunhold when you're standing on the bridge leading to Alinor palace. Feels unrealistic that the Altmer wouldn't build a road between them.
Ever heard of the trouble people in the real world have whenever they want to build just a short road through some nature reserve or similar area? I could imagine the high elves being even worse at this. Might even be a strategic choice to avoid the capital being easily accessible from all sides (and Sunhold as well).
Because Zenimax didn't think about it. I know that's not a satisfying answer, but not everything is meant to be explained in-universe
No one is saying there aren't multiple interpretations of the lore, and we're not arguing that ESO did it "wrong".
We're arguing that they decided to go for the most boring, mundane, seen-before interpretation possible. Like they almost always do, unless they can ride on the coat-tails of past games.