I'm A Banana
Potassium-Rich
I know there’s a bit of a mechanical difference between them in how the cast, slots, sorcery points, spell lists, etc.
I know there’s a membrane-thin fluff difference between them in one is born to power, one trades for power, and one studies for power. But that has effectively zero impact on the mechanics or actually playing one of the three.
But is that all? Even over a decade in to 5E and they just read like excuses to include different casting mechanics.
So fans of these three classes, besides the mechanics, what’s the draw?
How big does the difference need to be?
Like, Paladins and Rangers and Barbarians are just Fighters if you squint. Druids are just clerics. Clerics are mostly a variant wizard. Etc. Etc. Etc.
When it comes to class-based design, you are always somewhere on the Splitter/Joiner axis. The more Splitter you are, the more you see the unique aesthetics and names as worthy of new classes. The more Joiner you are, the more you want to have like, 1-5 classes that can Do Everything With The Right Options.
I lean a bit more Splitter myself, since I think a class label is a powerful psychological tool in play to achieve imaginary harmony. I'd rather be a Death Knight than a Paladin with the Death Knight Subclass, just because saying "I am a death knight" at the table is a powerful tool for putting an image in everyone else's head in a way that saying "I am a specific kind of paladin" does not.
As a consequence, I tend to think that D&D classes should be smaller, lighter, and more focused, and that there wouldn't be a problem with more of them.
So not only is there a difference between a sorcerer, a warlock, and a wizard, I also think that a pyromancer is different and a psionicist is different and a necromancer is different and a diviner is different and an elementalist is different and a shadow mage is different and...