You'd be a fool to be disappointed I think. The Final Fantasy franchise has always been about a new approach with every new iteration so if you have any kinds of expectations you are very wrong. The only thing you can expect is a quality game on every level and FFXIII was just that. You may not like the game but that's another story.
So if we think FFXIII was a bad game, we're wrong, right?
I do think it's a bad game. The level design is completely uninspired linearity. There's not even a hint of a meandering path off the main trail. It's nothing but move forward, get in a battle, move forward, get in a battle, move forward, cutscene. There's a reason JRPGs have towns for you to rest, buy, and save, and while the "let's not have any towns in the game" is sort of an original idea, it doesn't work at all.
Look at my last sentence.
And besides, people talk of linearity as if it's a bad thing but it really isn't. FFX was just as linear and it was never an issue, was it? Towns are so very boring and they don't add anything to the fun. Towns wouldn't work with FFXIII's storyline anyway. Also there is one town in the game actually.
I'm thinking you haven't completed the game because eventually you reach Pulse and that's when you get to explore more.
When you reach Pulse and realize that there's jack shit to do there (beside the genious XIII formula of run forward and press X), you reach whole new levels of the "WHAT THE FUCK WERE THEY THINKING" thought. God damn what a useless and bland expanse that was, and if that's what you find to be interesting, then your standards on exploration must be extremely low. The one that did free roaming right was FF XII (best of all of them). I spent a lot of time simply exploring it, as it was fun.
Towns wouldn't work with its storyline? Didn't stop our sweet party in FFX (you know, the famous and rebellious anti yevon pariah group). More like 1 town = 1 less polished CG scene, and in the interactive movie that is FF XIII, you can't have that, no. You have to shove your story down the players' throat. And a story told in one freaking sentence, to boot.
Ah, another diff with FFX is that.. you know... there was stuff to do there beside run forward, press X, and watch cutscenes. That is why the community and the reviewers are far less divided on that one (ah, and the characters weren't one-dimensional drones).
Wonder how they're gonna fuck up FF XV. The pre-order is out the window on that one.