The emulation of reality is a goal of many gamers both referees and players. It rages a lot for combat rules causing many to seek more "realistic" or interesting system. There is no real right or wrong answer. It is largely a matter of taste at how tactically detailed you like your combat or rules in general.
Magic also sometimes inspires these type of debates and it particular nonsensical there as you can make just about any damn thing. Call Chi, Psionics, the Force, Mana, whatever. Just make it a good design at the level of complexity you want.
Over the years criticism has been leveled at the D&D Vancian style of magic. Most alternative go as far away from memorization as possible and adopt some type of skill based magic system where limits on casting is how fatiguing it is or how much power it drains.
The D&D vancian magic system has a singular virtue compared to most of the alternative in GURPS, Rolemaster, Runequest, Harnmaster, D&D 4e, and so on. That is make sense that a faux medieval society would exist alongside a Vancian system of Magic.
For example, how do you deal with a GURPS Mage? By the raw rules, either you fight fire with fire and get another (hopefully friendly) mage or person that just happened to have a lot of magic resistance. Or get a bunch of mage willing to make you magic resistant items. And all of this leads to one thing. Killing the guy. If he has enough skill even ripping out his tongue, blinding him, or cutting off his hands won't be enough. Why? Because GURPS spells are learned skills that short of destroying the mage or his mind can't be stripped away from him.
The only real check in the raw GURPS rules is the fact that it takes a lot of points to be a mage and in GURPS skill points are a rough measure of how difficult it is learn. If society strips away the ability of the mage to spend the time training or teaching apprentices the problem could be managed.
In contrast all you need to do to a D&D magic-user is yank their spellbook. Sure they may have some memorized spells but without the spellbook they are all one shot effects. Plus unlike a GURPS Mage, it takes a high level wizard a lot of time to memorize the full spell tree. Especially in AD&D 1st. This makes the D&D magic-user far more apt to be a team player in society.
This is compounded by the cleric. They don't require spellbooks. Ordinarily this would be a dangerous thing but they only get this because they are pursuing somebody else's agenda. In lands that are dominated by less scrupulous gods the clerics are a force to be feared.
I baked the idea of clerics being dominant magic using class early on into the Majestic Wilderlands. The magic-users didn't get refined much until we ran the all-mage camapign in GURPS in the early 1990s. What a campaign that was.
Despite all the power that clerics get few players opt to make one. I think mainly because to be a cleric (or a paladin for that matter) means that most of the time you are pursuing somebody else's agenda not your own.
One interesting thing I learned about this throughout my years of refereeing is the art of manipulation with clerics and paladins. I mentioned in earlier posts that I work with players to develop backgrounds for their characters give them the context to adventure in the Majestic Wilderlands. For cleric and paladins this means they choose which deity to serve and usually had initial goals in align with the deities' ethos.
A typical approach would be the "Mission from God" where the referee has the deity keep feeding plot hook to the player. This I found to be a bit heavy handed and should be used sparingly.
Instead I look at what interests the player develop for his character and alter the various opportunities that come up to reinforce the fact he is serving his deity. The best moments come after a series of events are finished and the player realize he has been doing is what his deity wanted all along. It takes a light touch but it is really fun when it pays off.
Along with this I make sure that the character has plenty of contacts with the ordinary (and not so ordinary) people of his religion. I find this causes the player to start looking for opportunities to further the cause of the religion of his character.