I think their idea that a class should be able to allow for a large quantity of archetypes is deceptive when you look at some iconic class they put in the PHB.
Well, sure, if you try to walk all the PH1 classes past any sensible-sounding bar to new classes that would actually exclude the classes people keep asking for (check out the poll, they include, in descending order: Artificer, Warlord,
Psion(icist)'Mystic,' & Shaman.)
I'm about to join a new game and I want to play a druid because I love the theme of the class and they have access to my favorite spells list. The thing is: I probably wont play one in the end because the archetypes in the PHB inspire me nothing and WotC had a hard time coming with new compelling archetypes since then because, to be honest, the Druid class is a niche that doesnt allow for a lot of variation (even more when you force wildshaping in the core class).
So, if they are ok with the idea of a druid with 4 barely distinct archetypes with weak flavor differentiation between them, I dont think they should care if a new class can support 2 or 20 new archetypes, as long as the player base is interesting at playing the class.
Of the 5e implementations of classic classes, I have to admit, I like the Druid best. So you just had to go there. ;(
Considering the other bars proposed to new classes, the Paladin, Ranger, Barbarian, Monk, Druid, Cleric, Sorcerer, Warlock, and Bard would all run aground on any number of them. We'd be down to Fighter, Rogue, Wizard, prettymuch. Or 'Adventurer.'
Adventurer
...
The pyramid goes on and on.
The fact of the matter is... none of us need any of this stuff. When it comes to classes (and subclasses)... the only reason to make more is to placate the people who for whatever reason have to have a unique game mechanic attached to any and all story concept for what a PC is and does.
....Please. It was ridiculous then, and its ridiculous now. People multiclassing paladins, sorcerers and warlocks together for no other reason than uber-mechanical efficiency with Eldritch Blasts... character concept-driven reasons be damned.
If there is a STORY reason why a new concept needs to be a full class...If it CAN'T? Then there's no reason to make it a class other than a few people just wanting some brand new game mechanics to screw around with and graft onto other classes for MOAR POWER!
You seem to have two very different positions, above.
1) The game doesn't need new classes because you should be able to just build any new character concept by mixing & matching the existing ones, along with backgrounds, feats, and 'role playing.' (There's no psionic class? Just RP being able to read minds! "I can totally read your mind!" "OK, what am I thinking?" "You're thinking 'no way he can read my mind, there's no psionicist class'" "Wow, you CAN read minds!")
2) The game shouldn't allow MC'ing because it's total powergaming catnip, and every valid concept should just have a sub-class cover it - plus a background and throw in the 'just role-play-it' panacea for anything that's missing.
Which doesn't add up. I don't suppose you're just taking the apologist tack of '5e is perfect, any fewer classes (no Barabarian? unthinkable!) would be too few, any more classes ('psionicist?' bah! humbug!) would be too many,' so I guess I'm just missing an actual point in there somewhere....
As I see it: Yes, you can design a game with few classes - or no classes - and have players 'build' just the character they want, more or less from scratch.
Alternately, you can design a game with many (sub)Classes, each of which neatly fills out a given archetype or character concept, while leaving others unavailable.
If you do the latter, people who can't just pick a (sub)Class that neatly fills out the character concept they have in mind are going to demand new classes.
Since D&D has always gone with more classes, people who don't get what they want out of the existing classes want even moar classes. :shrug:
Mearls and Company have realized that game mechanics for game mechanics sake is stupid.
Then why'd they design 5e that way? 5e doesn't just use unique mechanics to define/differentiate some classes, it has some /sub/-classes that have unique mechanics assigned to them. "Don't add game mechanics for game mechanics' sake" ends you up with an effects-based system like Hero - and no classes, at all.