Personally, I find the vanilla system rather intuitive. If I want to get better with my blade, I use it. Think about this: If you take on a dragon with that sword, do you learn any more about how to use the sword then if you took on a bunch of goblins? You have taken on a much harder foe, but you swung the sword the same amount of times then if you have fought the goblins. They say practice makes perfect. I think it makes sense that you should have to do something many times to get better, instead of doing it perfect a couple times. You don't learn what doesn't work, only what works right then.
You really think that sword fighting is only about swinging the sword in the direction of an enemy and doing it often enough makes you a great swordfighter? That would be like playing a children's song over and over to become a masterful guitar player. I think a realistic way would be if you'd only gain experience points in combat skills if you were fighting enemies that are a challenge, depending on your blade skill. If you have a blade skill of 5 you might get an improvement by fighting mudcrabs, but if you have a blade skill of 50 fighting mudcrabs won't help you get any better. Doing a similar thing for all skills would be impossible though.
I use my healing spells when I need them, and I cast conjuration spells when I'm going to fight someone/something.
I have seen plenty of mods which I would use if I wanted a much more immersion based game. Ones that make it so you DO get more skill for using a bigger spell(magicka based spell training mods, for example, make it so you can't use a tiny training spell to the same effect as a master level spell), ones so you don't have the level up menu thing, ones that make all your stat gains fixed to certain levels based on your build.
Just because a system can be exploited, doesn't mean the system is broken. It just means that it has the potential to be exploited.
I've never spammed at skill other then alchemy(to get out of novice), and restoration(to get out of novice). And even then, I do it because I believe they either are useless at novice(both) or they level way to slowly(restoration), and I don't always do it.
Again, I disagree. If you can only exploit the system with some weird workarounds (aka glitching), that's okay. I think I could restrict myself from not using exploits in that case. But in Oblivion the system itself is a big, fat exploit rubbed directly into your face. I mean, you gain skill points by casting spells. So if I cast spells I'm using an exploit only because I don't
need to cast a spell right now? That is a completely broken game mechanic for me, not a potentially exploitable one.
The fact that you
can quickly level up to apprentice because you think novice level spells are useless is a clear sign for a broken game mechanic as well imo. In Oblivion XP (or any other games using XP) you have to spend some of your valuable skill points to get to apprentice level. Otherwise you simply can't use restoration spells or alchemy. That is generally another problem with Oblivion's default system. You can easily become a master of everything and all characters are the same in the end. You start with a Nord warrior, but at level 30 you are a powerful wizard and the greatest thief of all Tamriel as well. Not so with Oblivion XP. You have to choose which way you want your character to go. You might become a very powerful fighter, but then you can barely cast any spells and you aren't stealthy either. If you want to cast a bit of magic at least your combat skills won't be all at 100 in the end. Your choice. And that's what I like about it.