Why the desire for low magic?

[NigelWalmsley]

Sure, they have limits but the sheer versatility of magic mean that most casters can handle almost any type of situation. A fighter isn't capable of doing every kind of violence imaginable, a skill-monkey can't master every skill, why should a caster be capable of (almost) every kind of magic?

Why not? You're asking the wrong question. It doesn't matter if you can do every type of magic, or only one, or somewhere in between. It matters what range of problems you can solve with magic, and that's more a function of how long your spell list is and how you select spells than the range of things that are on it.

Yes, thematic classes are nice. I personally find wizards fairly boring in part because "I do magic" is a pretty flavorless concept. But it can also help with class imbalance, if every caster isn't capable of so many different kinds of magic. I'd prefer if they had to specialize, for both flavor and balance.

Consider the Necromancer. The Necromancer is, I think we can all agree, a flavorful class. You do Death Magic and you do not do other kinds of magic. But is the Necromancer any more mechanically limited than the Wizard? Not really. You can imagine just about any Wizard spell as a Necromancy spell, or at least a spell a Necromancer could cast. Bone blasts to deal direct damage, undead minions to take the place of summons (or even straight-up demonology), Magic Jar-ish soul puppetry to do everything Enchantment does, skeletal armor for Abjuration, undead craftsmen to break the economy, the list goes on. You can imagine a Necromancy-themed solution to pretty much every problem, and if you wrote as many spells for the Necromancer as WotC did for the Wizard, you'd get most of them. Conceptual limitations don't directly do anything to power. Insofar as they have an effect at all, it's a second-order result of more classes meaning less words for each class.

I agree that theming is better for shoving classes into more manageable boxes. The bigger point of contrast that should be drawn on the concepts each class is built around is their scalability.

That's the other thing. The Barbarian's concept is "like Conan". Even if you lock the Necromancer down not just to "Necromancy", but to a specific set of tactical niches (perhaps "minions, debuffs, and light blasting"), her ability to call on the souls of the damned simply scales farther than the Barbarian's ability to be strong.

It's somewhat funny to mention Malazan Book of the Fallen here since a lot of the series focuses on the ways non-magical fighters (the Malazan marines, especially the Bridgeburners) have developed ways to deal with magical opponents.

The Malazan Marines aren't really "low magic". They certainly have tactics for dealing with mages, but those tactics involve things like "their own mages" and "modern explosives". They're basically doing modern combined-arms tactics with magic. Also, the way the setting works is that if you are personally bad-ass enough (which is what's relevant in a D&D-ish TTRPG), you eventually become a superhuman Ascendant. A Practical Guide to Evil has pretty much the same deal with Names.

But if I understand your argument correctly then you're saying in a high-magic setting, everyone should play someone with magic. Which begs the question, since 3.x's concept is high magic, why are there non-magical classes in the first place? That question will lead right back to the "guy at the gym" problem that has been discussed a million times without any conclusion.

Because 3e's concept isn't just "high magic". 3e's (really, D&D's) concept is "zero to hero". And in that context, it's totally okay if some people are, or at least start out as, non-magical. Kaladin begins his story with the power of "good at spear". He does eventually get to fly and regenerate and have what is basically a lightsaber, but at 1st level it would be reasonable to stat him as a Fighter. The issue is that the game (except, oddly enough, 4e) doesn't have a good way of forcing the transition from "Spear Guy" to "Windrunner".

What bothers me about D&D 3.x in particular, however, is how it makes magic items feel like they get mass-produced.

I feel completely comfortable in saying that 3e's magic system is just worse than AD&D's. The game should go back to random magic items, and should eliminate the whole notion of chasing progressively larger bonuses.