Ye gods and little fishes, [MENTION=42582]pemerton[/MENTION] - put the can opener down and step away. You've let out far too many worms already!
I think this raises bigger questions about whether "the world of D&D" is meant to be generic, or particular. I see it as quite particular, and I see this particularity as also expressed via the alignment system.
The game of D&D, or its universe, I see as generic. Each particular game world is, of course, particular. That said...
Clerics, for instance, aren't just priests. They are militant religious types whose outlook and capabilities broadly reflects a quasi-mediaeval stereotype of the warrior-saint: undead and demons flee in their presence, they can call down blessings and curses, and they have power over serpents. Anti-clerics, on the other hand, do less healing but more cursing, and command the undead and demons. This set-up in turn presupposes a particular sort of cosmological set-up: gods of light, civilisation etc vs "gods" of death, destruction, corruption etc.
And also presupposes - wrongly - that there's such a thing as an "anti-Cleric" at all. There isn't. There's just Clerics of different alignments; and Cardinal Holierthanthou is mechanically every bit as much a Cleric as Cardinal Demonspawnfromhell.
Druids, by way of contrast, are quietistic, naturalist types who believe that human intervention (and the intervention of the divinities that humans serve) introduces destructive imbalance into the world.
This to me is a far too limiting interpretation of what Druids are or can be, and thus I tossed it some 3 decades ago.
Some ordinary Clerics (and every other class, for all that) can be quietist too, and some Druids can get right up in your face.
If one moves away from this underlying setting assumption, to include gods with the druidic outlook, and to make clerics and druids just special instances of the generic category "priests" - and by 2nd ed AD&D the move in this direction is basically complete - then personally I don't see the point of retaining the cleric spell lists, the alignment system, the rules for turning undead, etc, in their classic form.
Whyever not? Druids (a.k.a. Nature Clerics) can easily use the same framework as Clerics (a.k.a. Normal Clerics) and War Clerics, a third Cleric class we invented well before I started DMing. And it's in fact simpler that way; while also allowing for true Nature deities (of which, in Earth's history, there are a rather large number; Earth Herself is but one) to support the Cleric type that is closest to their sphere.
(Eg once things head in this direction, it makes sense to ask why animating the dead is evil at all, why good clerics need to be cautious about casting cause wounds spells, etc; because all those classic features of the rules system for clerics rest on setting assumptions that have been departed from.)
Er...no. Good is still good, evil is still evil (particularly from the absolutist point of view, my option 2 in a previous post) and the framework still holds up just fine. The only difference is that it's now possible to play a Chaotic Good Nature Cleric, or a Lawful Neutral one, rather than just being stuck in Neutral.
I think labelling automata and unintelligent undead (golems, skeletons, zombies etc) as TN makes less sense in this framework, as they are per se contrary to the natural order. I think it would makes more sense for them to have no alignment, just as most inanimate objects lack alignment altogether.
It's a very fuzzy line between Neutral and non-aligned. Golems tend to get lost somewhere in that fuzz.
A common means is isolation - living as hermits, or establishing small utopian communities. In D&D, druids fit this general description. This difference between druids - isolationist - and clerics - deeply engaged with human(oid) communities and the cosmological context and conflicts within which they are located - is one of the things I alluded too in my reply to @Lanefan upthread.
Again, I think you're being far too harsh in your pigeonholing of Druids / Nature Clerics. Druids can also be healers, herbalists, and so forth within a community; they can bless the sowing of seeds and the reaping of harvest; they can remind and-or educate city dwellers of the nature that is out there; and they can - if it suits their deity - spread the word of said deity to anyone who bothers to listen. (I have some deities ask far more than others when it comes to their Clerics promoting and advertising them)
Lan-"by far the best Nature Clerics I've seen are always either Elves or Hobbits"-efan