I think Adv/Dis is a very strong innovation, by the way, in that it is a rule that adequately folds in a bunch of stuff in a very simple, clean way. The type of thing that makes one wonder, "Why didn't they think of that before?"
In a sense, they did. When 3e consolidated myriad resolution mechanics into d20 vs DC; when 4e consolidated combat modifiers and conditions into Combat Advantage. Likewise, re-rolls, or roll-take-the-highest mechanics are nothing new.
Just as bounded accuracy is like the treadmill slowed down, Adv/Dis is a lot like CA, a non-stacking combat modifier.
I think you make a good point that when it comes down to it, 5E isn't that much simpler. But again, perception is key. A little bit goes a long way.
It's just smaller (though, for a new edition, it's got a lot packed into it) and more familiar. And, yes, perception is more important than reality in these things.
By making feats fewer but more powerful, 5E might reduce the total number to a fraction of previous editions, even in a few years.
Sure, changing granularity has effects like that. OTOH, it makes those feat decisions more critical - doubly so because you can't re-train, so it's back to planning 'builds' like in 3e.
In early 4e, there were not really must-have feats (a nice way of saying 'wow, none of these feats do much'), so you could take whatever fit your character, and not be behind the curve. The introduction of feat-taxes was more damaging, in that sense, then the proliferation of feats.
Don't forget the "auto mechanic principle" (or any technical, mechanical profession). What looks intuitive and easy to someone trained and knowledgeable is absolutely impenetrable to a lay person.
Exactly. By falling back on familiar structures, 5e feels intuitive to folks who have dealt with the originals for decades.
Well DM Fiat is always there, regardless of edition. But what I'm hoping for from 5E is something I found was lacking in 3.x, that I would have liked to see, which is what Mearls called the complexity dial. 5E starts at a lower "base complexity" than 3.X or 4E, giving a broader range.
Basic 5e presents a range of class complexity that exceeds even that in the 3e PH. The Champion fighter is dead-simple compared even to the 3e Barbarian, while the Wizard and Cleric are complex even compared to their tier-1 counterparts. I'm not sure if that's the point you were making, though.
Both 3.X and 4E forced everyone to play at a higher level of complexity, which worked many but not as much for casual players. This became exacerbated by system mastery issues, as I described in a previous post.
You really have to see new players trying 4e to believe how well it worked for them, and for casual play. It was deceptive, because it changed so much that, to an oldtimer, it felt almost impenetrable, but to new players, it was an open book - clear and consistent.
And, while it was, like 3e, hard to master, the rewards for system mastery were intentionally minimized, so you didn't have these balance issues with new players entering established groups or power-players bombing casual play.
3e and 5e, though, share a similar flavor of complexity, so it's easy to go from one to the other without so much effort. 5e's impressive achievement is that it's also pretty natural to go from AD&D to 5e Basic. AD&Ders somehow so out of touch that they've never been exposed to 3e MCing might blow a gasket when /that's/ introduced, but that's about the only obstacle.