Compared to the Falcon 9 booster, why is the Starship system's reusability proving inherently more complex?

Answer

The Starship system must prove reusability for both stages, with the Ship being inherently more complex due to reentry requirements.

The Starship system has the added complexity of proving reusability for both the booster and the inherently more complex Ship stage, which must manage atmospheric reentry requirements that the booster does not face.

Compared to the Falcon 9 booster, why is the Starship system's reusability proving inherently more complex?
AerospaceSpaceXrocketsLandingStarship