In terms of spells, Skyrim is missing a huge amount of spells.
Silence, Feather, Touch Spells, Open Lock to name a few. Open Lock is by far the worst spell omitted in Skyrim. It basically forces Mages to be a locksmith instead of a mage using magic to open chests.
If there's any spell out there that I would put back into Skyrim in a heartbeat, it would be open lock. It boggles my mind how Open Lock didn't make it into Skyrim. I would've thought the DLC's would've bought it back but we only get Waterwalking back and that's as a pair of enchanted Ancient Nord Boots (Ebony level strength) and Potion of Waterwalking, not as a spell. I definitely blame some of it on the date but the rest I blame on incompetence.