Then it becomes an unmarked quest? Just because it doesn't have a journal entry that says 'hey this is a quest' doesn't mean it's not a quest. There's not really much difference between an unmarked and a marked quests and it doesn't really change the fact that quests are pretty important in an RPG.
So, what does it have to have to still be a quest? What if it has no solution, nor reward?
Quests are generally an artificial construct. They are merely an aspect of broader world design and reactivity, and should be viewed in the context of those first and foremost.
While Skyrim's guild questlines are arguably bad (mainly due to length, but also some severe logic problems), individual quests aren't really below par. There is also decent amount of integration present - for example two bandits involved in pale lady quest were originally running with a group of bandits from another hideout and had to flee following failed mutiny - you know, details, crumb trails, that sort of thing.
It may not be Morrowind, but even in Morrowind quests only really worked as a part of broader context - most would be pretty awful in isolation.
Also, faction questlines may be derpy in Skyrim, but they do a better job providing tangible rewards than in Morrowind:
College of Winterhold? Be able to unlock access to top tier spells via respective rituals.
Companions? Be a werewolf.
Morrowind factions definitely had better pacing, more internal logic, and were more down to earth, without obligatory epic story arcs, but lack of membership benefits was effectively a running joke with them.
Turn into a vampire and you think you've hit a dead end - but even putting the game's 'backdoor path to victory' (killing Vivec) aside, if you find the clan home of the vampire that turned you you've got another chain of quests open to you - which also seem to hit a dead end. You've been told by the game and by its developers in interviews that vampirism can't be cured in Morrowind after you complete the transition, so...game over right? Hang on - if you've been paying attention to the various libraries, you'll have noticed that there's a couple of books on vampires, one of which suggests that a 3rd volume contains a way of curing vampiricism post-turning. The first 2 books are relatively common, but the 3rd is rare as fuck (I think it's a once off, from memory) - so you have to either stealth or massacre your way through the libraries of Vivec and the various Houses to find the 3rd book, which then tells you the location of the one place in the game where you can cure vampiricism post-turning (you've got basically no chance of stumbling across it by accident - and if you did without having found the book, you won't know what it is anyway).
Nothing in the 'marked quests' tells you about the books, or that you should look for the 3rd volume, or that you should find the place it descrives - it's all just there in-game. And it beats most of the marked quests hands-down.
One of Skyrim's problems is that this kind of stuff would be marked in it and divided into quest stages and whatnot.
Also, it's two books and there is a quest leading to them - one for MG.
One thing that was good about MW is that quests often intertwinned or had multiple entry points.
Still, the quests have always paled in comparison with other aspects of the game.
What do you think about SkyRe?
I used it briefly, but it was always too restrictive (lol, can raise only humanoids with necromancy) and convoluted for my taste, and then it started doing deep arbitrary changes to various aspects - illusion, trying to make restoration into image of divine magic from D&D and I jay Wilson'd it.