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.
My experience was quite different than yours. I've introduced many people to D&D over the decades, and even the most casual player was able to wrap her head around playing a fighter within minutes. With AD&D or B/X D&D, I could tell a player to roll some dice, write down these numbers, and the rest of us will explain the rules as we go along. By the end of the first combat, pretty much every player had the basics down: roll d20+2 to hit, roll d8+2 for damage, AC means how hard it is to hit me, when I hit 0 HP I'm dead/unconscious, and I can move X squares on the grid on my turn. That covers most of the knowledge needed to play a fighter for a long time, other than saving throws, which you generally only need to know about when something happens to you.
Introducing 3e to new players worked out pretty much the same (but pick feats like Weapon Focus for the player), plus critical hits and provoking AoOs. AoOs often took a long time for players to understand.
In both of the above situations, the player can generally make in-character decisions each turn in combat. Who do I want to attack? Where do I need to move in order to attack? Am I hurt enough to retreat?
Even the simplest character in 4e (human slayer) requires the player to become familiar with a lot more game concepts. In addition to the concepts mentioned above, this player will quickly need to understand:
- temporary hit points
- healing surges
- the bloodied condition
- at-will vs encounter powers
- 2 stances and 2 encounter powers (Power Strike and Second Wind)
- action points
- forced movement (push vs pull vs slide)
- tracking round-by-round +/- X modifiers to hit/damage/AC/etc
- combat advantage
During play, the player needs to now track three separate measures of a character's durability (every new player I've introduced 4e to has asked me why this is necessary). The simpler combat stances give static bonuses to hit or damage, so the player needs to note the modified attack and damage values for each weapon in each stance.
The focus on teamwork in 4e means that other party members are using powers that let him spend a healing surge, grant him temporary hit points, grant him combat advantage, or grant him a +/- 1/2 to hit/damage/AC "until the end of his next turn."
The player of a fighter in AD&D, B/X D&D, or 3e can remain mostly concerned with his own character's abilities and the subset of rules that are involved.
The player of a fighter in 4e has to interact with a larger subset of rules just to cover his own character's abilities. On top of that, monsters will frequently impose forced movement, short-term conditions, and short-term penalties to hit/damage/AC. Being a front-line combatant, his character is one of the optimal targets for the leaders' various fiddly "until the end of your next turn" buffs and tactical adjustments.
Everyone else's actions more or less impose more complexity on that player's gaming experience, through constantly shifting battlefield positions, short-term conditions, and round-by-round mathematical adjustments.
That was my experience with 4e and new players. Now, my sample size is small, and I've gamed with a lot more new players in pre-4e than in 4e, so I cannot claim to be representative. When I read the 4e rules, I was really excited and everything was very clear and consistent. But in play, every new player in my groups complained about these same issues (as did some of the experienced but lapsed players). They all expressed the sentiment that, as soon as combat started, they felt like they were just interacting with rules instead of playing characters and interacting with the world.
I haven't played 5e yet, beyond a couple of sessions using the first playtest packet, but it definitely seems much closer to the first experience than the second.
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.
I agree with that. The issue that I found wasn't a balance issue but a conflict of expectations and preferences. The new/casual players didn't want to deal with a lot of complexity and too many decisions to make, so they tended to play strikers. The experienced players loved the tactical depth of the system, and tended to play leaders or controllers. So the casual players stick to using their simplest abilities while the experienced players keep giving them "until the end of your next turn" buffs that the recipients don't want to deal with and sometimes trying to make "optimal" decisions for them.
So in my (admittedly limited) experience, 4e didn't work well at all for casual players. The clear and consistent rules were overshadowed by all of the factors that they had to consider at each decision point during play.
We may have different definitions of a casual player, however. I'm using the term to describe a player who plays in a regular or semi-regular game but his or her involvement with D&D ends when the gaming session ends. The player doesn't own any D&D books, doesn't read anyone else's D&D books, and essentially doesn't even think about D&D when not playing.