If there's one thing wrong with Raising Arizona , it's a lack of sympathy. The Coens don't seem to care about any of their characters, except as the butts of jokes. Really effective slapstick depends on the audience caring about the disaster befalling the characters, but if the filmmakers don't care about them, the audience won't, either. The Coens made Raising Arizona with too much brains, and too little heart. Blood Simple was all thought and no emotion, too, but the thriller genre is inherently more cerebral than comedy.
Good comedy comes from the gut and the heart, only secondarily from the brain.
Given its immense uncertainty of tone, I'd have to rate Raising Arizona as a failure, overall. But it is a very different type of failure than the typical film. Raising Arizona is an imaginative failure, a failure caused by an attempt to do more than the filmmakers really knew how to do. That may not be the same thing as success, but it's more interesting than some films that achieve everything they set out to do. For those looking for something different than the average film, Raising Arizona is worth seeing.