There was a pretty notable dislike for the loss of random battles (something I personally don't care to see the return of) at the time of FFXII, if I recall correctly, and I actually feel FFXIII does it better than most. You could argue for or against having a separate 'field' for battles, but I think that with the design of FFXIII's fields it worked decently in the end. SE were trying to find that middle ground between random battles and FFXII's MMO-like style, and I seem to recall people going on about how it was managed to avoid random battles while still allowing a battle field to be generated in a Chrono game and I believe that FFXIII ended up doing just that. In the end, I feel SE are damned if they do, damned if they don't when it comes to a lot of things and battle random battles (I-X) vs. fixed battle fields (XIII) vs. MMO-like battles (XII). I can see the merits of all three options, personally, and the downsides. I don't know which I like best, but it's probably something between FFX's style and that of FFXIII.