Being a mage in Skyrim sounds like it's going to be incredibly powerful and fun (placing spells on the ground for enemies to walk into and trigger like traps, structures catching on fire and burning with actual effects on the economy as a result, etc.) and the revamped combat in the game seems like it was thoroughly planned and executed for concrete reasons, with this being one of the natural results of balancing it. It also sounds like being a pure mage is going to be quite different from being anything else in the game.
I don't personally feel like I'm losing anything by not being able to create spells, given that acquiring more powerful versions of spells will still be possible through alternate means, and given that we cannot combine different spell effects this time regardless of how we do it (creation OR dual-casting.) People have long complained that mages are overpowered, too. Perhaps this is a response to that criticism. (Although I suspect it has more to do with technical limitations and clear design choices.)
But I do wish it was in for those who feel they just have to have it.