Question

Why planets are more complex than stars?

Answer 1

Both of them are complex, they're still just big balls of hydrogen with a few other elements thrown in. Planets are far more complex in terms of composition, even the gaseous ones. They may rival the stars for dynamic complexity, we don't really know enough about either yet to be sure. Rocky planets like Earth are relatively static by comparison, but far more varied in composition than gas giant planets or stars.