I could make links to numerous reviews like this one, saying that this particular game powered by the apocalypse, or that particular game powered by the apocalypse are terrible. But that would just be cherry picking the various sites, blog posts, forum comments, and other elements of the internet that fit my views while ignoring the numerous other opinions which state that these games are wonderful and innovative.
I really wish I could find the post where Vincent Baker claimed that he wanted a game where only the rules as written were the game, anything else should be expressly forbidden from being added to it...for pure genre emulation you shouldn't need anything else. But after a couple of hours searching, I can't find it at all.
Instead I have found something of his that I like, and particularly a comment by Ron Edwards below it.
The basic gist is that a game is like a lightbulb above a table. The whole scene is uolt up in layers. The filament of the lightbulb is the essence of the game, the fundamental core mechanisms of play, tightly wound, burning bright, creating the deepest experience. The glass of the lighbulb is both illuminated by the filament, and allowing light to pass through it. It acts as a lens in certain ways, or there might be patterns painted on the glass of the bulb...either way it takes the core mechanisms light and modifies it for use in a variety of situations. The combined filament and glass are basically what you buy when you purchase a game from the designer.
The illuminated table is the play experience provided by the game. It's everything you bring to the session (physically and metaphorically), which isn't a part of the ga e rules. Maybe you shine the light in different ways to tell different types of stories... perhaps if the glass around the filament is tinted red, it might not pick up on nuances between greens and blues on the table, the game just isn't designed to do those things. Maybe the glass is painted in elaborate and organic swirls, and when it casts it's light on your gridded tabletop you just end up with a psychedelic mind-fuck. It's not really right for the story you want but it'll give you a hell of an adventure anyway.
The rest of the room is the entirety of experience and world that could potentially come into the game, but hasn't yet manifested in play.
The inner layers affect the outer layers, but the outer layers don't necessarily affect the inner layers. The filament produces the specific intensity and temperature of light regardless of what is around it. Changing the filament changes the whole experience, everything is lit in a different way, and even if everything else is the same it might look generally similar but there will be something subconsciously, fundamentally different about it. Changing the glass affects everything outside the bulb, using the same filament in a new glass shell is reskinning or hacking a game. It's not particularly hard to paint your own patterns on the glass, but making a filament is trickier...making them work together is trickier still. Making changes to the table is what everyone does during play...every table and every group is different, they may shine the light in different ways to get their stpries happening, they may argue about the best way to shine the light, but as long as they're all using the same type of bulb from the same design team, they're all playing the same game.
It's an interesting analogy, and I could probably push it even further. But that will do for the moment.