It is hard to continue with the old ways of games. Think about it, as a business in the present, you tell a player to walk around a 2d world where the characters stand still and wait for you to punch in a command and you might as well be locking up your doors and stop making games.

Players today want action, graphics, and movement. Companies know that the long time fans will continue to play, but they also want fresh gamers to purchase their product as well. FFXIII and the sequel allow for the fans who are new to the world of RPGs to play a game that introduces them to how these types of games are played. After all, the point of some of the trophies is to beat a particular boss as fast as possible. I know that if that were the case in FFVI and FFT, Square would not have been around to merge with Enix.

Understanding that it is a new world of gaming that old players have to adapt to the new ways. Anyone know a person who refuses to use computers because it is too new to them? It is the same way. Comparing games to the old consoles should not happen. Take each console and see how the games have evolved. SNES and PSX FFs were turn based ATB with the focus on story and battle systems. PS2 FFs focused the new technology to create a world that was visually stunning to the player, but sacrificing in the battle systems to do that. If they didn't have raging fans beating down their doors for new games, they might have been able to change things. PS3/360 (ugh, i hate xbox) is where the new wave of games are now. Give it time, I imagine that there will be at least two more FFs for this generation of consoles. They always come up with a unique battle system for each game (or set of games since FFXIII looks like it still might have another).

Point being, they had to do something that would be different in the sequel that was not in the original. There has not been an FF where the "world map" was a grid. They also set up a world that has yet to be explored if and when FFXIII-3 would come out.