Like the title says.

As each game (since Daggerfall) has been released, they've been removing a lot of the RP, customization and simulation elements in order to make things more convenient for the player. Some people have called this 'dumbing down', while others have said it's 'streamlining'. I'll admit, there have been a lot of cool features removed that didn't break the pace of the game, like spellmaking and whatnot, and I'd like to see them return. At the same time, they've been adding a lot of cool stuff, too. What do you think?

Spellmaking.

Enchanting scrolls

Attributes, separate armor pieces, a larger array of summonable creatures, attributes, something vaguely similar to the Classes, spellcrafting, spears, other marksmanship weapons, attributes, Ax/Long and Short Blade/Blunt being separate skills, speechcraft mattering again, the unarmored skill, and decent cultural representation.

Did I mention attributes?

One absolutely fundamental item that was removed: Possible Failure. In early TES games, you succeeded or failed according to the character's stats, not the controller skills of the player. For an action game, the change is acceptable or even desirable, but if a dexterous player can succeed despite the total absence of skills by the character, or a player with poorer reflexes fails repeatedly despite the character having 100 skill in that category, then the game fails completely as a RPG. You're not playing the character, you're playing "yourself" every time, and any differences between characters are relatively meaningless compared to player skill.

In Arena, Daggerfall, or Morrowind, if your spell casting skills are low, and you try a difficult spell, you have a chance to fail, and gradually get more proficient at it as your skill increases. In Oblivion and Skyrim, you can't even attempt a spell that's one point above your ability, yet succeed at it every time without fail once you gain that single point. The first three TES games were based around "learn by doing", the latter two are "succeed because you're the special snowflake".

Attributes are heavily tied to this, and are badly missed by a lot of players, particularly those who RP.

Incidentally, I'd also like to see the return of Spears from Morrowind and Climbing from Daggerfall. Just for the sake of asking, why couldn't I buy a Colovian Fur Helm in Colovia?