So... Extra Credits has a good video on this subject as it relates to video games, and it applies to tabletop games as well! Having actually played a full game of Age of Sigmar now, I feel that I can now adequately discuss what the primary differences between Age of Sigmar and Warhammer Fantasy are.
It boils down to depths and complexity. I have a friend who complains about how tabletop games are simpler these days and how it's a bad thing. Well, the overwhelming reason for the trend towards simplicity in game design is actually driven by an aging consumer base who finds themselves with much less time to game than they used to. Or as I've put it; there's a period of time between 'graduating college' and 'The kids have moved out' where your gaming time is rather limited. But I digress.
Warhammer Fantasy Battles 8th Edition is unquestionably a complex game. So are the 6th editions and 7th editions of the game, which I've played. There are rules for seemingly everything that could crop up in a game (although it is not BattleTech or Star Fleet Battles, whose writers have spent considerable time analyzing edge cases and ensuring that they are covered). The rules are detailed for a game that is more about marching blocks of infantry across the board and smashing each other to bits. The trend for the game was to add complexity in the hopes that it would add depth, which as Extra Credits points out, really limits the players' experiences of depth.
Because if you were a new player, you had to slog through all those rules and edge cases before you could understand what a useful choice was. And let's face it, learning to play a game with a rulebook that could probably stop a bullet or two is intimidating to most of us. It was the second barrier to entry the game had, after the sheer cost to get started. So when you add in the large ruleset to the cost of entry, you end up with a product that deters new players from starting because they're not sure if they'll enjoy playing before they sink a few hundred dollars of cash into it.
It certainly hit me when I tried to play WHFB. I also saw the light in many a prospective player's eyes die when they looked at the rule book and the amount of money they'd have to sink to start playing. Usually the next question was: What's this War Machine and Hordes stuff over here? At which point we'd make a sale on a Hordes/War Machine starter box. Meanwhile the Warhammer Fantasy range would gather dust on the shelves.
As any company can tell you, if you can't get new consumers to buy your product, you're probably stagnating or losing money.
Age of Sigmar was a very brave choice for Games Workshop to make, and I feel it was the necessary one. Is Age of Sigmar a complex game? Not at all. But it does have depth as Extra Credits would put it.
The depth is hidden though; it is certainly not in the four pages of How To Play. Instead the writers at Games Workshop have placed the game's depth and options in the unit rules and the many scenarios published for the game. It is now a game that competes with other modern miniature games because as of this writing, Games Workshop has produced 'starter sets' for a fairly good price. $85 and the cost of printing your unit rules plus the four pages of rules out. You could get away with a single unit box, but you would actually be selling yourself short by doing that because you wouldn't get to see the interplay between command abilities and the troops.
And the interplay between models is a big part of where Age of Sigmar's depth comes in. Have your Lord-Castellant use his lantern on a Lord-Celestant and watch your opponent complain about 2+ saves on a model that tends to smite things dead. Kill some Wrathmongers and watch your models murder each other too. It's all very interesting to see in action as opposed to reading about it.
I also think the reason that Games Workshop offers no points or balance between forces other than model count is because of the scenarios. The scenarios are varied in that sometimes each side has a different objective and sometimes they are not really fair to one side. So there is that challenge of overcoming the handicap or trying to complete an objective. Your own model selection can make or break a scenario for you, so you are rewarded for trying the same scenario with different units and tactics.
Personally, I'm alright with Age of Sigmar's lack of complexity and rather happy about the depth it provides. The game is one I enjoy playing, as opposed to feeling like a real chore like how Warhammer Fantasy felt.
Though I agree with a friend of mine that I do like relative weapon skills. At the same time, the fixed weapon skills do make things flow a lot faster.
Yeah yeah, call me a GW apologist or shill if you want.