Miyazaki and Takahata had opposite theories of what animation is for

The "Miyazaki is fun, Takahata is serious" framing misses the actual split. The real difference is about what animation can do that other visual media can't.

Miyazaki uses animation to show things that don't exist and can't be photographed: flight, spirits, wind made visible, worlds that require a drawn line to inhabit. For him, animation escapes the limits of live-action. Takahata runs the opposite direction. He uses animation to get closer to real experience than live-action can manage: a girl peeling a persimmon with the wrong rhythm of someone not really present (Only Yesterday), a child's hunger without an actor's face to soften it (Grave of the Fireflies). For him, animation removes the actor's body as a buffer between the audience and the thing.

Dimension	Miyazaki	Takahata
What animation reveals	Things you've never seen: flight, spirits, wind made visible	Things you've seen but never looked at: chores, weather, a meal
Subject	A child, a mythic landscape, a moral test	A family, a historical moment, a social process
Time signature	Adventure arcs with quiet moments inside them	Long stretches of dailiness; drama emerges from accumulation
Production model	One-man army; recruits young animators he can shape	Collective; assembles veterans he's known for decades
Source material	Original or loosely European (Heidi, Earthsea, fantasy)	Japanese folktale, postwar memoir, ethnographic fiction

Source claim: Miyazaki uses animation to show what can't exist; Takahata uses it to show what you've seen but never really looked at.