Here's the thing that you and the other "Druids should be Spellcasters, first and foremost!" are failing to address for we who do not feel that way. What, if anything, distinguishes "Druid" from just "Nature Priest with specific real-world cultural trappings and practices"?
The Druid as a spellcaster in D&D has been pretty much obsolete since at least 2nd edition AD&D, when "Nature Priest" was a niche opened to clerics via kits and Spheres, and their obsolescence was cemented via the Domains mechanic.
All that defines the "D&D Druid" as being seperate from the Cleric is the fact it has spellcasting magic AND shapeshifting AND an animal companion. Cut it free of everything bar the spellcasting, and you have nothing that convincingly and meaningfully distinguishes it from a Nature Cleric with a larger alternate spell-list- at least, nothing that you have shared so far.
Simply put, appealing to "tradition" has no meaning and is not a convincing argument when the end result of doing so basically portrays the Druid as nothing more than a Captain Ethnic take on the Nature Priest. Especially given arguments like "Nature Clerics can turn undead and Druids shouldn't be able to do that!"
...Excuse me? Servitors of the holy earth mother should not be empowered to put an end to creatures that mock the natural cycles through their very existence? Just... think about that for a minute or two, see if you can't see the problem with it.
So what should you and the other "Druids should be Shapeshifters, first and foremost!" be required to address for those of us who feel differently about the druid? Have I been playing my druids wrong, or I daresay with
badwrongfun, if I have deemphasized their shapeshifting in favor of their spellcasting?
What distinguishes a wizard from a sorcerer from a warlock from a bard from any given arcane class here? Don't you think that placing their "distinct thing" in opposition to their spellcasting is absurd? Especially if it meant getting rid of their spellcasting in favor of their "distinct thing"? They all get 9th level arcane spells (in 5e)! You may call that tradition, but it's a tradition that distinguishes between sorcerers, wizards, bards, warlocks, and other arcanists.
I don't think that just because a druid has wild shape as their unique thing means that the druid should be reduced to wild shape any more than a wizard should be reduced to a spellbook without their spells. If anything, if the druid and nature priest are that redundant, then I would say that they should be combined such that their role as a spellcaster is preserved. Or, perhaps more obviously, if the druid and nature priest are really that redundant, then why not remove the nature cleric subclass?
Even apart from wild shape, there are some fairly huge differences between clerics and druids, especially if one looks at the spell list. (And this is ignoring other iconic traditions such as armor and weapon proficiencies.) The nature priest really only gets a small smattering of the spells that makes the druid a druid. What's a druid without Entangle? Does a nature cleric have that spell? Nope. Goodberry? Nope. Faerie Fire? Nope. The nature cleric has a few iconic druid spells, but in order to turn the nature cleric into a druid, you would have to greatly expand the cleric's base or domain spell list. The overall flavor of their respective spell lists suggests that the nature cleric and druid are two entirely different "nature priests" to the point that calling them both "nature priests" may just make them superficial "false friends" instead of archetypal cognates. Sure that's a "larger alternate spell-list," but that's a hefty "larger alternative spell-list" and not some trifling few spells here and there as you so easily dismiss it as being. If you really have to make that much larger of a spell list for the nature cleric (and not the other clerics) to recreate the druid, then that speaks volumes in and of itself. I also like the analogy that someone made earlier of Arcane Cleric : Wizard :: Nature Cleric : Druid.
Although 4E offered a more constrained view of the druid, to borrow someone else's phrasing, it also placed the druid in unique niche apart from the cleric. The cleric was a "divine leader," whereas the druid was a "primal controller." The 4E roles themselves, in some regard, don't matter too much and contribute to that aforementioned "constrained view," but the shift from the "divine" to the "primal" power source for the druid felt like a meaningful shift. And I will admit that despite the switch to 5E (and its restoration of old terms), I still regard the druid's differing emphasis to be "primal" over "divine." I suppose what has been seen can't be unseen. This is what I see as the critical difference between the nature priest and the druid. The nature priest serves nature deities, drawing power from them (or however clerics do). The druid may revere deities, but their power ultimately comes from the primal power of nature itself. Nature clerics represent the aspect of nature as expressed through their deity's portfolio, but druids represent the full primality of nature.
