I think the fact that XIII had the weird auto battle combat also made a lot of people hate it. Ironically, the mix of roles that you could switch into throughout a fight made it, imo, a more complex and skill based combat system than most prior final fantasies. Most of the earlier final fantasy games were just "pick attack over and over again, use your biggest nuke spells instead when fighting a boss and heal when needed." For some specific enemies you might use a single buff or debuff that was relevant to that fight.