My nine year-old daughter occasionally plays in my Dwimmermount campaign when she's not distracted by other activities. Her character, Iriadessa, is a 3rd-level magic-user. She's frequently confused by the way that spell levels don't map on to character levels. I have to admit I share her frustrations. Although three decades of playing D&D has made it second nature to say "Oh, you have to be 9th level before you can cast 5th level spells," it nevertheless rubs me the wrong way.
If I had my druthers, I'd probably rework the spell list so that spell level corresponded better to character level, but I suspect it'd take a lot of work to do right and, even then, would somehow not feel right. Anti-intuitive this convention clearly is, but it's such a longstanding one that changing it would probably step over some imaginary line in my brain and push it toward the dreaded category of "not D&D." Funny how that works sometimes.