This is the main crux of the entire matter and I think is the easiest for me to answer.
We found out in 4E that class name matters to many people. In many cases, moreso than the mechanics of the class.
It's been said before... 4E was designed such that the mechanics to run an archer PC fell into the 'Ranger' class name. You wanted to be an archer... you were supposed to use the Ranger mechanics. If you didn't want to be a "nature" based archer, the game told you to just strip the Nature stuff out (heck, it even let you select Dungeoneering rather than Nature as the 'free skill' you got), and refluff it to whatever kind of archer you wanted.
And many people HATED that.
They wanted to play a 'Fighter' archer. Not a 'Ranger'. Not even a refluffed 'Ranger'. A 'Fighter'. One who was an archer. And what made it doubly troubling was that a 4E 'Fighter' was actually a tank, and it was exceedingly difficult to make it anything other than a Defender tank. And that pissed people off. WotC assigned specific mechanics to specific classes, and folks went nuts. Because they now could no longer choose for themselves what their Fighter did... it was hardwired into the game.
And that is exactly what it looks like WotC is trying to fix with 5E.
If WotC was to design the game such that if you wanted to play 'variant mechanics module X' you had to play some other class rather than the class you wanted to play (all in the effort of trying to establish some type of 'class identity')... they would be making 4E classes all over again.
And we know exactly how well that went over with a large percentage of the population.
While I fully agree, I think you are missing the forest by the trees here. One thing is saying "I want fighters to be able to be good tanks or archers or skirmishers" or "I want sorcerers to be able to be blasters, buffers, illusionist, tricksters, melee warriors or not having nay spells related to combat at all" and "I want wizards to have either spellpoints, mana, recharge, aEDU, Vancian or spontaneus casting", the first two are humble requests of not being shoehorned into doing only one thing by your class, the other one is a request of not being shoehorned into a single mechanic you don't like. Both are very different things.
For example as a sorcerer fan all I ask is for them to have a single yet flexible and
simple spellcasting mechanic that captures the "inner magic" feel of the class, I don't care if it is spellpoints, slots, roll to cast or recharge (ok I'd hate it if it was recharge as it is slightly biased towards combat), as long as it is simple and allows me to convert the two dozens or so of diverse sorcerers I've played over the years. If on the flipside I'm forced to "follow this contribed process to get something resembling the simple caster you want, but there is no warranty you'll get the support to make it flexible as the phb is crowded with options, and gameplay is complex anyway, oh and at the DM whims you may be forced to play something far more complicated". Reluctance to pick a single mechanic for sorcerers will hurt the class as much as the straightjacketing of the class did in 4e.
Or with the rogue, so far all rogues having sneak attack has been something bad for many players, having a way out of it sounds good on papper, but when it becomes "you can trade out sneak attack for yet another way to make damage, oh and sneak attack now is way weaker in order for it to be balanced with everything else under XD, and all the defaults include sneak attack anyway", really if that is the alternative I'd rather have kept mandatory sneak attack for all rogues, a single ability is easier to ignore than a whole subsystem. (And I'mstarting to see the creep wizard-seep sorcerer all over again just with fighters and rogues, you cannot balance a class to cause damage at will with another that only does it situationally by just giving the second one the same package with reduced numbers in the same way you cannot balance having potentially unlimited knowledge over the universe with only knowing a handfull of spells if the later has the exact same estructure than the former just with lower numbers).
Part of the problem I have with the current approach is that it will rennounce having a simple default on all classes in order to answer many questions and requests nobody has made just because many people have speciffic requests on speciffic classes. Just because it is a general demand that wizards and fighters have differing levels of complexity it doens't necessarilly imply every other class has to be shoehorned into that mould too.
