Some of those I dont recognise but, Harry Potter? Their spells never fail and are also ridiculously easy to cast. Star Wars? When did a force power ever not succeed and Darth Vader hilariously fail to force choke someone. Discworld? The only Wizzard that cant cast is Rincewind but that is the whole point of the character carrying around one of the worlds most powerful spells. Conan? Just finished the Tower of the Elephant and there were no miscast spells in that.
Ron Weasley, Neville Longbottom (especially their freshmen and sophomore years) and the fact that there is a well-used nurse's ward in Hogwarts would argue with your "never fail" appraisal of magic in Harry Potter. Many full-fledged wizards can't successfully cast the
Patronus charm and other magics, potions class was regularly depicted as a circus of failure. (Although I agree that the spells are often depicted as simple and swift actions, especially in the movies.) And that's not to count the number of spells that simply miss their intended targets.
Several Jedi fail at the Suggestion ability or have it go sideways. Luke also fails to levitate the X-Wing. There is the general failure of the Jedi Prescient ability to detect the Sith or a planetfull of clones being trained into an army. Luke tries to summon Ben at the end of Empire (at least in some edits), but then turns to Leia when that fails.
The Discworld Wizards demonstrate laughably (it is a comedy after all) inconsistent magic. So much so that they avoid trying to use it whenever possible. The Librarian is a fine example, or perhaps I should just say "Ook". One of the wizards in Lost Continent "loses control" of a fireball. Its unclear whether BS Johnson was using magic or just unearthly engineering.
The consequences of a miscast (or perhaps poorly conceived) spell and the are the central thread of the plot in the Earthsea trilogy.
Mythological nearly everyone has magic whether it be creatures like elves, goblins or leprechauns or humans like Morganth or Circe.
I was restricting myself to human casters. Although I suppose one might look at Elves, given D&D. Then again, elves are quite varied in their depiction in legend ranging quite aways from the D&D depiction. Morgan and Circe do some shapeshifting, artifice, and illusion, but I don't recall anything similar to D&D combat casting.
From your list Harry Potter, Star Wars and Discworld.
Erm, those aren't exactly pre-D&D, and I disagree with your assessment.
From Appendix N we have Michael Moorcock, Fritz Lieber, JRR Tolkien and Jack Vance
I'm fine with Vance, couldn't say for Lieber or Moorcock. Tolkien, though? Its unclear whether any mortal "casters" exist. (Although certainly there are mortal artificers and craftsmen that can access some kind of magic, and its unclear exactly what counts as canon or not.) Nonetheless, these sources are "modern" in the sense that they come after artillery was a common experience.
Personally, I just can't see how having some sort of Casting Check to use a spell would break D&D any more than having a Fighter make an Attack Roll or a Rogue make a skill check does, with added benefit that we could look at dropping Vancian casting. I certainly don't see how it would somehow make D&D inconsistent with fantasy literature (outside of Vance, perhaps) or unfantastic.
