Auto-attack was a godsend for me but that is mostly because I have to deal with lag so typically my attacks would be less frequent than most people's. Melee classes can reuse skills and accumulate TP fast enough to be always doing something in most battles so if they had to press attack every time as well it would be too much and they would have to stop fighting entirely to type something. Magic classes are close to this, however, since I don't think mages ever use their auto-attack or even engage their character during combat.

It's a fine system for combat but it only fits into games with the same theme as a whole.