Exploring would be for quests, equipment (like daedric armor, and there would be a small chance of someone wearing it), gold, looking for grand souls, training your combat skills, etc...
Invisibility potion.
Ok nobody forces me to look it up, but once you find an item you'll know where it is the next games. You have to assume every single aspect of the game will be attempted to be abused, so that argument isn't valid. That was what Morrowind showed: easy money (mudcrab, creeper, many expensive stuff just waiting to be picked up), easy to get powerful artifacts, 5x attributes (which gave a lot of work and was boring for many people). It's immersion breaking if you know an artifact is in x place or you know there is an easy way to make money and then you don't use it. If that character was you, wouldn't you want to get easy money and powerful items?
Random generated open world is generic, boring and doesn't give much feeling of reward, this goes for enviroment, leveling and loot.
Quests are just as premade as handplaced items.
Then nerf insibility potions, not the item system that made Morrowind the greatest open world RPG to date.
As I already stated, it takes several playthrough to fgind everything, so you wont automatically know where everything is.
The problem with easy money was the creeper/mudcrap merchant, not the handplaced items, this could just as easily be exploited with random generated lloot.
It's not immersion breaking to know where stuff is, it's just a result having been replaying the game over and over again, that's like saying it's immersion breaking because the mainquest is the same everytime, not valid.
Who's talking about easy to get powerful artifacts, we're talking about well-hidden, well protected, cleverly placed artifacts that makes the experience feel rewarding.