Ridiculous D&D contrivances

[JonestheSpy]

I mean, there must be a few Orc tribes who aren't as barbaric, or at least neutral.

No, I don't think there's a 'must' there. Could be, depending on the campaign, but no compuslion.

The "always evil" thing just doesn't work, especially for creatures that aren't "the incarnation of pure evil".

Sure it does.

Are all red dragons jerks?

Could be.

Are all white dragons wild beasts that attack anything that can't obviously kill it?

Unless they're unusually intelligent.

There have to be variations in behavior.

No, actually there don't.

As I mentioned in the dwarf/elf alignment thread, the above posters are thinking in terms of science fiction, not fantasy. Fantasy is about dream, archetype, overarching meta-reality. You don't need to think about personality deviation among orcs and dragons, they are what they are. Pure evil and pure good don't exist in real life, and they don't either in fiction that emulates real life - even in non-existent settings - but they do in fantasy. That's kind of the point.

Now that can easily lend itself to BAD fantasy and boring, cookie-cutter creatures and settings - you need to have reasons behind things, definitely. Tolkien's monsters were evil because they were created by the Satanic deity Morgoth - either corrupted from other creatures like the orcs, or lesser evil spirits given form like the first dragon. They are motivated by his will, and naturally act out of hate, spite, malice, and greed.

Now you can have a world where all the races are just different species trying to get by in their various ways, and the endless copying of Tolkien and the boredom thereby generated certainly can encourage folks in that direction, but there's no must about it.