TESO is still mostly a themepark MMO, you get to a new area, with its own theme and issues, you solve them, and move over to the next one.
Since one Tamriel hit, things changed a lot, now we're able to go anywhere and do any quest we want, indeed making the game feel more open world in a sense.
But there's still the fact that everyquest pretty much takes you right next to it all the time, so you still solve things per area, instead of having to go to other places.
An idea would be to change just that, to make the game feel more open world. having sidequests taken in some place, but that require you to go to a totally different place, maybe even on a different map, change the scenery, change the setting. I know there are a few quests like this, but it's really few and in between. most of them are "please go to these ruins RIGHT next to me, and then come back to me, please."
Speaking of quests, another thing that could help break up the monotony would be to unclude crafting in some quests, have some quests actually require to craft something (and I mean regular quests, not the specific crafting quests with no story in cities) of course it would need to be somthing that anyone can craft, nothing that requires a high lever or anything.
These are just some ideas that I think could make the questing experience a bit more varied and not a constant monotony of "hero help me", "thanks" *walks 2 steps* "hero help me!"
