There is too much magic in modern fantasy gaming. It is everywhere, in most subclasses; some classes are entirely magic, and it is magic, magic, magic everywhere and all day long.
It gets tedious. Nobody can be skilled at anything anymore. You need the magic crack to do anything.
AD&D 1E featured anti-magic fields, creatures, weapons, and even planes. Put any modern D&D 5 characters there, and they will be helpless. There is too much magic in the game, setting, and universe. It isn’t high fantasy anymore; it's ultra-fantasy and magic overload.
Some of the old modules had lists of spells that were not allowed to be used in certain dungeons, and too much magic was a problem back in the early days of D&D, too. There were dungeons where a simple passwall spell would ruin the whole thing, the Tomb of Horrors being one of them.
I doubt there are many 5.5E classes that aren’t magic-touched anymore. Look long enough, and every class has to have overpowered magic options, which begs the question: Are you anything without magic? Do skill and non-magical training matter?
Magic in D&D is like sex on the Internet: it's everywhere, there is too much of it, and I am tired of it all.
In Old School Essentials Classic Fantasy, four of the seven classes were non-magical. In Advanced Fantasy, eleven of the twenty-two classes are non-magical. That is about half or more of the classes have no magic whatsoever. While there are magic items, half of the classes themselves are entirely non-magical. The game is set in a low-magic world, which is the norm.
I could easily play OSE without magic; you can do the same with both BX and 1E. It wasn't a problem, and the game had enough to it that removing magic would not feel like you were losing too much.
There is so much magic in fantasy these days that it does not feel like "magic" at all; it feels like power entitlement and magic being used to prop up weak class designs and lackluster combat options. The amateur game designer uses magic as a crutch. If your game works without magic and is exciting and engaging, you've got me.
The default setting for fantasy should be a low-magic world. This keeps the game grounded and believable. This is also the reason humans should be the default choice for races, since they are the most diverse and familiar race to which we are accustomed. I find that in a game where everyone is forced to play humans (ACKS II being the best example of this), we get a wonderful diversity of cultures, whereas in fantasy games that allow the typical fantasy race selections, the diversity of the average tiefling, dragonborn, or dwarf is actually quite low, and they fall into stereotypes and parody way too often for my tastes.
In GURPS, I have the freedom to create campaigns without one bit of magic at all. I can play a historical game without being weighed down by magic, witchcraft, divine magic, nature magic, or planar interference. Not all humanoids are magical, elemental, or fay, as they are in D&D 5.5E. I can create a compelling fantasy game with not one iota of magic in it. I can craft authentic fantasy campaigns based on real historical settings.
I don't have to default to a multiverse planar setting at all.
I can play a pirate game in the Age of Sail and not worry about a mage flinging fireballs at the other vessel. Use the cannons, please, you aren't a cannon yourself. I know, that's not fun, but in a game where I expect my scurrvy dogs to be able to learn how cannonry works, what is the point if half the party can fling equal death from their fingertips? Use the cannons like a pirate and stop complaining, or you are walking the plank.
Better yet, without magic, players have to drill down and focus on melee weapons, how to fight, archery, thrown weapons, special attacks, advantages that give them the edge in combat, weapon reach, defenses, and attack and defense actions. The flow of combat becomes the "magic" in the game and the key to victory. Knowing how to fight, stacking the odds in your favor, and never giving the enemy a chance are your "spells," and there is no easy solution to a fight.
Players need to pay attention to the combat system and rules to do well, and they can't lean on spells or special powers to save them. Thank you, finally, sanity is in my game. Immerse yourself in the world and realistic fighting techniques and tactics, and you will find a much greater satisfaction in mastery there than you will in casting an infinite-use cantrip every turn and being bored with your choices.
Too common magic isn't magical.
It is the mundane and the everyday.
There is no mystery or unknown.
And it becomes boring.


