Elimination of certain kinds of items, such as thrown weapons, crossbows, and spears
This touches upon the most important sucky aspect of Oblivion is that its combat absolutely sucks.
I've returned to Mount & Blade, Dark Souls and even to Dark Messiah of Might and Magic many times for the sheer fun of combat. Can't say I ever enjoyed killing a single mudcrab in Oblivion. It's so boring, it breaks immersion.
books less interesting than in Morrowind
Half of the books have literally been brought over.
But this touches upon another interesting fact: how often have you gone out of your way to look for 200-300 word stories in real life? They don't exist. Short stories/novelettes range between 1k and 20k words, but 1k word is an outlier. More often it's ~7k or more.
I'm not the biggest reader of speculative fiction, but I've read some, and I actually can't recall a single good short story the length of a Morrowind book, except "They're made out of meat". And it's in form of a dialogue. Maybe if we all pitch in, we'll come up with a list of 10 such stories in all of human history of writing.
Morrowind books range from 200 (!) words to 1,5k. And the problem with them is that they're actually trying to be "books".
Compare to Fallout 1-2. You find a pre-war computer and read some "newspaper articles". You're excited - finally you're going to find out how the world ended. Because you've been playing this game for 40 hours and have no idea - it's an old, forgotten mystery. Or you break into someone's computer in Deus Ex or VTMB and read their "personal email". You find out their dirty secrets, it's taboo, it's fun.
When you've been playing Oblivion, there's no mystery. You don't actually "need" anything from a book. You open one with very little hope for anything, and it's the life of some saint, or an infodump on Telvani, a description of the Nords, etc.
Then, if we delete all this drivel from the game (which the designers should've done), there is a couple of books that are either "useful" or "entertaining".
The "usefulness" in them is they tell you where some shrine is, and how you can summon some daedra that you kill easily and who that drops nothing. It doesn't affect the world or you. Wasted time. Maybe you'll know Morrowind/Oblivion better than me, I'm sure you'll be able to name one example where the usefulness was actually on display, maybe even two examples, but then those are the only two books that should've been in the game.
The "entertaining" ones fail to entertain, because of the format. You can't build an engaging narrative in two words. You can't build it in five hundred words. And especially you can't build one when you're a paid per hour wagie.
Successful examples of "interesting text" are Deus Ex, VTMB and Fallout 1/2.
But even giants like BG1-2 fail with their book selection. Books trying to be books in games are simply a bad idea. You want a book, go pick one up at a library.