Sorry, I'm not reading through that. The level system in Oblivion is badly broken, so if that's where you're getting the restrictive nature of the class system from, that's where you're having a problem understanding it.
Back in Daggerfall you did not gain 20 levels by maxing out a single primary skill and enemies did not level with you. As you progressed through the game you naturally ran into more and more difficult enemies. If 10 levels down the road you decided to go from a heavy armor sword and board user to a pure caster, you went to some random low level dungeons, ground out some skills, and carried on. If you do this in Skyrim, you're screwed. Drop 10 points into the 2H tree and you have no way of getting them back. Drop 10 into 2H, drop another 10 into 1H, another 10 into archery, and there's no way to continue as a pure caster without a significantly gimped character. I hated Morrowind so I can't remember for certain, but I believe Morrowind had the same leveling system as Daggerfall. For whatever reason they changed and botched it badly in Oblivion, which is one of the reasons they changed it again in Skyrim.
The class system is designed to advance you in levels as you gain skills, with more experience being given for the primary skills. As you level you're gaining ability points and health/mana/stamina. Outside of that it wasn't supposed to have any impact on the game. For whatever reason Oblivion significantly reduced the amount of skills needed per level and set the entire world to level with you.