No they aren't. The first game they played any role in at all was Oblivion, and it was still just a side quest. The five preceding games barely mentioned them.
"Just a side quest" is how you describe the ultimate quest of the Thieves Guild and breaking into White Gold Tower?
Well yes. How else would you describe it? There's the main quest, and then there's every other quest. Every quest that isn't part of the main quest is a side quest. And quite frankly the TG quest line was terrible. "I have this cursed magic doodad that has screwed up my life! How do I fix it? Oh I know, with
another magic doodad!" *yawn* It's the same thing as with MW and Oblivion. The Dark Brotherhood quest line is about loyalty, madness, vengeance, and betrayal. The TG quest line is about magic doodads.
Anyway, the preceding games had them in the background, but Skyrim having some contact with one isn't a bad thing. It's completely appropriate for the story in Skyrim's case, because as I said before, Skyrim's story brings Fate into the picture. In TES the only ways to alter Fate are through the direct intervention of Daedra or Aedra or through the use of an Elder Scroll. You aren't even the one altering Fate, that was done way back when Alduin first tried to eat the world. The Dragonborn's usage of the Elder Scroll is just to take a look at what was done with it before to learn Dragonrend, which for an artifact of the Elder Scroll's power is fairly mundane.
Like I said, it's a matter of opinion. My opinion is that using it in Skyrim was a bad thing. As you yourself said, you use it in a very mundane way. IMO that really cheapens it.
Something being mysterious doesn't make it interesting. Mysterious things can be interesting, but some mysterious things are just plain unknown, like the Elder Scrolls were for most of the series.
Um, mysterious and unknown mean pretty much the same thing. But you're half-right, simply being unknown isn't enough to make something interesting. It also has to be important in some way, which the Elder Scrolls clearly are, what with being in the title of each of the games.
Futhermore, we still know almost nothing about them. All knowledge about the Elder Scrolls is as follows:
-They are the oldest things in the universe.
-They are capable of changing Fate.
-With them you can see the real past and all potential futures.
-You cannot grasp the true form of the Elder Scrolls.
-People who don't know about the Elder Scrolls do not react with Elder Scrolls and just see what looks like a weird star chart in some unknown language.
-People who know about the Elder Scrolls but are untrained to read them will see a future and be stricken blind by it.
-The Ancestor Moths can train people to survive staggered exposure to the Elder Scrolls, vision partially intact.
-The training of the Ancestor Moths only does so much, and eventually the reader will go blind.
-The Dwemer developed a machine that could read Elder Scrolls before they vanished, and there was one in the machine when they vanished.
-Elder Scrolls are uncountable and any gathering of them will fluctuate in number for no discernible reason.
And most of that requires some intentional lore searching to figure out.
And that's "very little" knowledge, is it? For a magical artifact, that's actually quite a lot. We're of course never going to know how they work simply because the answer, however wordy, is always going to be "by magic". But I find that what you've listed is more than enough information already. What also bothers me a great deal is that they're supposedly these extremely powerful items that can do anything from breaking daedric curses to sending dragons forward in time, yet you can't actually
do anything with it when you have one. "Oh but your character doesn't know how to use it," says the game. Well then why can't I bloody well go and find someone to teach me? I had the exact same issue with the Heart in Morrowind. I have Kagrenac's Tools, I'm in the Heart chamber, why is my only option to destroy the Heart? Why can't I make myself a god like the Tribunal and Dagoth Ur did? Vivec didn't tell me how to do that, he only told me how to use the tools to destroy the Heart, but why can't I ask that dwemer? He was a big shot working alongside Kagrenac and there are dwemer books lying around with illustrations of the tools being used to manipulate the Heart. Surely he could help me figure it out. But no, the option to ask him about it isn't even there. IMO the player shouldn't be able to get their hands on these immensely powerful artifacts if they then won't be allowed to use them meaningfully.