Except you forget that VI also has a class system and relic system which were both introduced fairly early in that game. VI also throws you into several scenarios that gave the player a limited amount of control between choosing where the story was going (when the party gets split up on the Lete River not to mention the Lete river itself and all the non-straightforward dunge0on designs) and it constantly introduced new characters that brought in new playstyles all the way up to the point when it "opened up". So I don't feel the older games are as bad as what some reviewers have been complaining about.

XIII reviews are talking about how even a leveling system doesn't get introduced until a few hours in and some have hinted the full extent of the Paradigm system won't unlock until somewhere between the 50% and 70% mark in the game. The issue of how the system opens up is one of the few elements I'm really concerned about cause frankly the battle system is about the only thing I'm really looking forward to. It will be a shame if it goes FFX's route and doesn't come into its own until the game might as well be over.