Well this is a topic sure to get me salty. Of course, this might not be the right place to discuss it, as I fear that it might turn into a circlejerk; we are all Key fans for a reason, and I’m sure none of us wouod be key fans if we couldn’t accept such a big part of the series.
Now then, does Key magic exist? Yes; yes it does. Granted the most recent Key works have shown the magic fairly early on, but I feel that doesn’t defend it from the naysayers who are quick to judge.
But the important question: Is Key magic a form of deus ex machina? For that I give a big NO. So what exactly is a deus ex machina? It’s when a sudden unexpected and/or unexplained factor is introduced in the story that helps the characters solve the problem. It’s been argued fairly many times that “Key magic isn’t unexplained” or “there has been ample foreshadowing” but I think the reason people still find that hard to swallow is because it’s still very open to interpretation. Some people would still deny the power of the (clannad spoilers) orbs of light despite having read the VN.
That being the case, if the solution really is unexpected, then what stops it from being a deus ex machina? It’s the second part of the definition: “solve the problem”. And that’s what people fail to see in Key works. In Clannad, the problem isn’t to try to make Nagisa alive; the problem is getting Tomoya to realize the importance of his own family and that is solved through a very realistic way. To give a more timely relevant example, in Shiori’s route in Kanon, the problem isn’t to find a way to get Shiori to survive; the problem is to get Shiori to realize the importance of her own life, which is, again, solved through a very realistic means.
So to those who say that Key is guilty of deus ex machina, to that I say, you simply aren’t aware of the real problem. You focus too much on the physical problems of the world, and fail to see how characters are people that have more complicated internal problems that they need to solve. The physical problems being solved are nothing more than bonus endings, and in many cases, are even something that you have a choice whether to pursue or not.
All that being said, I just hope this post of mine helps some other people who fail to see the real problem of key stories, and helps give them a new perspective on how to view these intricate stories crafted by Key.