doctorbadwolf
Heretic of The Seventh Circle
There's no issue, as long as every character is distinct in both mechanical representation as well as the in-game reality corresponding to those mechanics.
It's perfectly fine, for example, to have a nature-cleric right alongside a druid. There just needs to be some objectively identifiable in-game reason for why they have different powers, and why the druid can't wear metal. You should never have a choice about which mechanics to fit to the character. You should be able to tell your DM all about your character's backstory, and your DM should be able to tell you 100%, without a doubt, whether that's a druid or a nature-cleric.
I think I might understand your general outlook slightly more now, but mostly because of that last line. You seem to be operating under the impression that the player's input regarding the character should mostly just be the concept, and the DM and the mechanics of the game should do the rest, where I believe strongly that the character should be as much the exclusive territory of the player as is practically possible, within whatever campaign restrictions exist for a given game.
Right now, the Ancients Paladin and the Ranger can both be used to represent nature revering protectors, whose devotion is rewarded with magical power. They both have a lot of potential out of combat utility, and can bring some serious hurt to their enemies. But they are mechanically distinct, because there are just naturally multiple ways to represent that character. And of course the Cleric is just a slightly more priestly Paladin, and I've always thought it should be more priestly in order to better distinguish it from the Paladin, and also because the priest who just isn't going to kill anyone, ever, and has never worn armor or swung a weapon is kinda harder than it ought to be to represeent well in the game.
But the other thing is, the mindset that values fewer options and as little overlap as possible leads to things like the druid never getting made, because there's a nature cleric. And that's a bad thing, because the druid better represents the concept than the cleric does, even though the nature cleric can represent the character fairly adequately.
But when you refuse to have overlap, or have multiple ways to represent a single concept, you miss out on the benefits of tailor made mechanics, which are great. In the end, I just think that the issues you raise are just vastly less important than players having solid representation of their characters, with mechanics that aren't being jury rigged, or reflavored, or whatever in order to pretty much represent the character.
When there are only three classes, yeah, there's never any doubt where a ranger sits (except that there will be, because some people think it's a fighter and others think it's a rogue, so, hey, maybe only two classes, eh?), but the ranger also isn't going to be terrible well represented, unless each class is complex enough that it might as well be a framework in which multiple classes exist.
And as we see with the 5e design and some of it's subclasses, some concepts end up as watered down versions of themselves because a subclass can't replace class features from the base class, and some concepts work best with mechanics that should be the central feature of a character. Of course that could be fixed by making subclasses a bigger percentage of the class than they generally are, but that's a whole other discussion.
IDK, this got ranty. Sorry. I guess I just disagree with your stance so fundamentally, and...just in every facet of it, that it's hard for me to even grok it very well.