The mediocrity as I understand was from the rift that developed in the team about the vision of the game being a sandbox vs a campaign.

However, I witnessed a new divide among the team which was less well-known; as more core game developers (such as myself) were recruited to help finish the game, a cultural gap emerged between the newer ‘gameplay’ team and the older ‘Sim’ team. The former group (which went on to spearhead Darkspore) was primarily concerned with how Spore played as a game. Were the mechanics engaging? Did the player’s choices matter? Was the game replayable? In contrast, the ‘Sim’ team carried the traditional Maxis DNA and was more comfortable with Spore as a toy box. Could the players express themselves? Was sharing one’s creations with other players meaningful? Did the game spark the imagination?

These cultural divides ruined Spore’s chances to be a focused, cohesive experience.

http://www.designer-notes.com/2013/09/