I don't agree with this at all. Some of my concerns about traditional D&D spellcasters being overpowered arise from straightforward uses of spells like Charm/Dominate Person, Invisibility, Fly, Polymorph, Teleport, and a whole host of Divination spells. These are the spells that, playing AD&D, have led to broken builds and that, playing Rolemaster, my group nerfed so as to tone down the caster/non-caster imbalance.
I find Teleport is often interpreted more loosely than the actual spell suggests. The GM doesn't want to make waves, so that bad percentile roll comes to nothing. We can "study an area carefully" through means whose ability to allow the area to be studied carefully is suspect, the PC's have no difficulty all joining hands in mid-combat, etc. Charms and Dominates are often envisioned as "well, he made his save so life goes on - no offense taken" and the rules for detecting a person is charmed or dominated are simply ignored. Invisible casters are able to forcefully speak their verbal components and no one notices, lose their scent, etc. Flying ones are assumed to be removed from the field of combat.
Divination seems to vary a lot group to group. The question of how the divination spells lead to the perfect knowledge claimed is one that never seems answered. Polymorph, however, has been an issue, and has been amended numerous times in the hopes of fixing it.
The big picture issue is often "oh, we can arrange a rest and come back tomorrow at our leisure - go ahead and Nova". The rest of the world should not enter stasis for 23 hours because the PC's blew off all their spells at the start of the day.
Now, I certainly noticed we seemed overpowered against Goblins with our Sorcerer's sleep spells at low levels. Guess what? Not all opponents are affected by Sleep spells, and he has a limited, though large, number each day. Issues also arise when the opponents have similar HD to the PC's and the monsters close for melee.
I feel that way when people who dump cha get ignored no matter how well they 'role play speeches' so I understand.
I just "love" rousing, persuasive speeches from 8 CHA characters. Perhaps the best response is "That was highly persuasive content, delivered effectively and passionately. I can only assume Grunk the Horrendous is a spitter." Of course, one can also simply use "Nice delivery - obviously your own Diplomacy roll is much better than your characters. Roll his Diplomacy to see how well he emulated your excellent speech."
That doesn't mean a bonus for use of good intel would not be awarded - that's in-game. But the fact that my player is a skilled orator does not make his 8 CHA character with no social skills a better speaker, any more than the fact he is also morbidly obese and must pause to catch his breath twice to climb the basement stairs means his nimble (if anti-social) rogue is impeded from doing a Kirk shoulder roll, spinning out with twin daggers in hand to disembowel his enemy, then backflipping away, nimbly landing on his feet. And let's not talk about role playing whether you make your save against that Lightning Bolt!
The Wizard is also supposedly manipulating the cosmic forces of the universe in ways they aren't meant to be manipulated. It might possibly be considered difficult enough to have a failure chance.
Sure. I'm not saying that the failure chance cannot be a very workable balancing mechanism. I am saying it is not the perfect solution which will work for all groups.
Also, plenty of people injure themselves with weapons every year. Any assumption that weapons are easy to use without injuring yourself is not backed up by evidence. The Fighter gets away with swinging an axe around in combat because of years of training.
Yet those characters with minimal or no weapons training also have no risk of self-injury, or even harming comrades. And didn't the Wizard spend years of training to learn to manipulating the cosmic forces of the universe in ways they aren't meant to be manipulated? Why is the fighter to be competent in his field of expertise, but the wizard should blow it on regular occasions?