This is my take on it.
A class is picking a set number of skills/attributes that define your gameplay from the beginning.
Only if you don't have any imagination. If you do have sufficient imagination, then a class is nothing more than a set of inclinations and talents that might or might not correspond with the skills you'll end up using.
The only people who are bound by class are those who can't think beyond whatever it is that the game gives them.
Skyrims system is the exact same thing, except you don't pick it from the beginning, you pick it as you GO.
If you pick it as you go, it's not the same thing. You don't pick talents and inclinations as you go - you already possess them. You pick skills as you go, which is the same thing you did in past games. So the skills - the things you pick as you go - are there now as they were then. The rest of it - the talents and inclinations - are simply gone.
You define your "class" as you play, you learn your class, and you create your OWN class based on what skills you use.
Within the context of skills, again, that's what you always did. But now your "class" won't have the added flavor of talents and inclinations. It will ONLY consist of skills.
Want to play a Mage? Use magic, no armor, daggers, and staves. Voila. Guess what? You're a Mage. RP and imagination required, but that's how it should be.
Again, that's how it's always been. But in the past, you could play a mage who wasn't particularly talented at it and had to rely exclusively on skills, or one who had a great deal of innate talent and could coast on skills, or anything in between. Now, ALL you can do is practice the skills. All the rest of it is gone.
Want to play a Warrior? Use swords/axes/maces, heavy armor, smithing, and have a beard. Voila. Guess what? You're a Warrior. RP and imagination required, but again, that's how it should be.
And again, that's how it's always been, though again, talents and inclinations are gone and all that's left are skills.
Which, I guess, is fine for the people who can't roleplay a character who's anything more than the sum of his skills. Some of us, however, can and would rather play characters who are a bit more than just an accumulation of skills.