"(This is, of course, entirely ruined if all the spells are explained in painstaking detail in appendix III of the game manual.) Great wizards like Gandalf and Obi Wan (orig. trilogy version) are intruiging to a large extent because the reader/viewer has no idea what the extent and nature of their powers are. "
Horrible examples. Books/movies don't come with game play rules that the player/viewer can know. In games, there's a set of rules/guidelines for this kind of stuff so unless the DM 9ie game devloper) 'cheats'; there'll be a lack of mystery in that regard for us players (notwithstanding if we ecounter spellcasters more pwoerful than our controlled characters).
That why D&D magic doens't have the 'mystery' you want because there are rulebooks detailing how said spell system works.
It's a game. It ahs to have game play and hence rules. And, as a player, I'd like to knbow the rules before I play. This is different, of course, than having to know everything about everything.
"That rather depends on how you define 'low magic' doesn't it??"
And, like I said, it's not gonna be low magic. My standards for that is too high.