You don't really stumble upon it though. You know what it's going to be, just not what it looks like (specifically, anyway). It doesn't encourage exploration as much as it encourages discovering pre-approved places. If you're walking straight down a path, and you see that there's a ruin to your left, you'd probably turn left because it showed up on your compass -- even if there's an amazing waterfall just ahead with a pot o' gold at the base. It would have been better if places didn't show up on your compass unless they were marked on your map first.
Why? Why shouldn't there be meaningful consequences? It detracts from character development and gameplay experience when Bethesda makes it so quests can't be failed (even if you don't intend on doing them) or certain NPC's can't be killed (Todd Howard: "No, you can't role-play a murder! You have to keep that person alive just incase you want to be a magician! -- but you can't be a good magician either because you spent too many perk points on becoming a murderer!").
It's pretty much Bethesda saying, "You're playing the game wrong." How can that be in an open-world RPG like Skyrim? It just doesn't make sense.
Also, there's the journal. I know that's a hot subject on these forums, and people certainly have mixed views on it.. but quests aren't nearly as meaningful when they're displayed as simple objectives on a list (and by simple, I mean simple -- most of them couldn't get any more vague or literal). Morrowind may not have had the best way of doing things (according to some people), but it was headed in the right direction. Oblivion basically fell of a cliff in that aspect, while Skyrim only succeeded in climbing 1/4 of the way back up. It's not an MMORPG. Objects don't need to be short and literal or vague. They should be full of detail (only the details you're given, mind you). Same goes for marked objectives. If someone wants you to go to dungeon x, but they don't specifically tell you where it is (or even that it's a dungeon), it shouldn't automatically appear on your map. The kind of depth and detail in the quest system has greatly diminished since Morrowind (the fetch this/kill that quests in Morrowind had a storyline and plot behind them half of the time -- but even when they didn't, they made since.. no newcomer to any guild or house is going to be sent on important missions at first, for instance).
They aren't in Skyrim either - Did you even
play the questlines, or are you just repeating what others say?
Companions begin with a routine "Show us what you're made of" quest. Then you get a routine quest "Lets see how you do with a partner" - and THEN things go wrong by having the Companion's "Dark Secret" revealed too soon. Also, you handle yourself so admirably in that mission that it's apparent you're the hottest thing to enter Skyrim since Ysgramor.
The College of Winterhold starts with you having to demonstrate the Uselessness of Wards, and then you're forgotten and can't do anything because the [censored] ward will always fail before Tolfdir shuts up and actually casts the [censored] fireball at you, thus hitting you and breaking the quest. Or, you prove yourself the most awesome mage ever by actually managing to hold the ward up for that [censored] long (Seriously, Tolfdir needs to learn how to
shut up), and you're
still given the most menial job (Picking up trash, essentially) on an expedition that
all Apprentices are invited along on. Once you find an artifact, the [censored] Psijiics step in and screw everything up because that's what elves do.
The Thieves Guild has natural progression, until you
prove yourself to be the Hottest thing to enter Riften since the entire Supervolcano area first erupted.
The Dark Brotherhood has the Night Mother playing favorites, because you're the coolest thing to enter the sanctuary since Sithis.