I spent ages in Morrowind just walking about, squatting in swamps, picking herbs and experimenting with them. I liked that blunt, sword and axe were all different, that short and longswords were different. I liked that you could fuck around with enchanting and if you were good enough at it you could create shit that let you fly, or make a Hulk ring, something that'd increase your jumping and give you a bit of levitate, so you could bound across the world. I also loved the fast-travel system that was in the game, ie: the strider things.
Like, even if they didn't want that sort of thing to be able to be done in Oblivion there were plenty better ways to do it than totally gimping the skill system. From the very beginning I was looking for mods to fix things. Arrows and magic flew way too slowly, both at and away from me. Magic was gimped to hell. You had to hit everyone/get hit a million times in combat, and your shit broke too often. Torches were completely useless, because you could see well enough in the dark. Traps weren't scary because they'd just hit you and bounce off with a little damage.
I appreciated the weapon mods that made everything hit harder and last longer, the arrow speed mods that made archery more dangerous, magic rebalancing mods that made facing off against mages more than constantly advancing while sidestepping their pathetic attempts at harming you, and both the darker nights/dungeons and more dangerous traps mods for doing exactly what their names would lead you to think. I remember testing out a trap after applying the dangerous traps mod and seeing my dude get killed with one hit from a big fuckoff log with spikes on and thinking "ok yeah, now that's fucking great"
I hope that they have some way of looking at the sort of mods people used and taking them onboard as suggestions for what people want the new game to be like, but I seriously doubt it.