I think that if the colours were perhaps a bit brighter or more colourful that would have helped things.
I get everything you're saying except this. All the other Miyazaki films you mentioned have a much darker palette than Ponyo. I thought the colors were
too vivid at times.
I guess I should stress for anyone who hasn't seen it yet that
Ponyo is a kids film that happens to be very nice to look at, which is different from saying that it's a kids film that has adult appeal. It's not
Spirited Away, exactly. This is a movie for young children, in fact it's pretty much tailored for them. In other Miyazaki films, the rules of the world are set up fairly artfully and expressed through the plot and the many sumptuous visual setpieces.
Ponyo in many instances tells and doesn't show - How magic works in the world is largely explained through expository dialogue, spoken to no one in particular or to someone who obviously already knows what's being said - a setup not unlike much of the pop anime that Miyazaki usually sets his work apart from. It can get sort of jarring for older viewers, but children probably won't mind. The cleaner, simpler animation suggests a cleaner, simpler sort of movie.
There is a certain dreamy, childlike quality to the whole film. Mostly you get the sense that very little, if anything, is happening outside the confines of the screen. There are scenes featuring a severe storm yet there is no destruction or any apparent risk of injury. When the main character and his mother elect to drive directly into the storm, the storm seems to be specifically following them as in a nightmare. Largely because it is actually following them, at least in part.
One detail in
Ponyo that identifies it as Miyazaki is that unlike in most western fiction, magic and imagination are not things that are exclusively under the purview of childhood. The heros and heroines of Miyazaki films tend to be children, but there exist no skeptics in these worlds - It was not a little baffling to watch
My Neighbor Totoro for the first time expecting the father to scoff when his children tell him of their encounter with forest spirits and see him not even humoring them, but immediately accepting their tale as fact. Similarly, when Ponyo arrives at the main character's house as a human girl and they tell his mother that she used to be a goldfish, her reaction is essentially "Well, stuff like that happens sometimes, let's eat dinner." Also worth noting is that, as in most all Miyazaki films, there's no "villain" to speak of.
Overall the pace of the film is quite easygoing, there's very little in the way of action throughout, and one's sense of wonder is not
constantly being fed like it would be watching other, richer Miyazaki films like
Spirited Away or
Mononoke (though scenes like the one in which a deep-voiced wave monster gets tickled by hundreds of goldfish-girls belong in the canpon), but there's still a lot to recommend it.
It's also sort of funny that they got Matt Damon to VA and yet he's got maybe 10 lines in the entire movie.