Does anyone really want to play a game where Lightning goes on routine patrols in a peaceful city, then comes home from work and fights with Serah? Or playing Team Nora as they cause trouble and hang out at the beach? Or play Sazh as he picks up his kid from school and shops for a baby chocobo for his birthday? Or Hope doing homework, going on field trips at school and hating his dad? That's really all that happened before the game started in the Episode Zero stuff.
The flashbacks show Serah and Dajh getting turned into l'cie, Snow's wedding proposal, Lightning's birthday; this isn't super critical stuff. The game started at the first major event, the Purge. The only thing we really missed was seeing Serah wander into The Vestige and get turned into a l'cie.
It started in a very similar way to FFX, with heavy action immediately. No one knew what the giant water orb was, what blitzball was, what Zanarkand was, who Auron was, or what Sin was. You didn't find out until much later in the game. Everyone was cool with it, so I don't really get the complaints honestly.
FFX didn't spend 20 hours flashing back with cut scenes while almost nothing happened in the present tense gameplay. It spent that initial time exploring the world of Spira, and did so without requiring datalogs for a basic understanding for the story.
As for those flashbacks that essentially built up FFXIII's story, SE could've just written a storyline that didn't require hours of non-interactive exposition just to get you started. The storylien setup they have here was, from the standpoint of being told in a game, flawed from square one.