I kind of have to wonder about the age group doing most of the complaining. I can't imagine it was wholly the younger generation of gamers. I'm almost inclined to suppose to the old DQ fogies decided they wanted the game to stay the same as when they played it two decades ago.
I did think it was weird for a main entry in DQ to experiment with another battle system entirely, especially when the series has been so stylistically consistent. Still, it would have been a change welcomed by me. Maybe we'll see it again in another spinoff title.
Also, the Japanese of all people whined about the change? Shocking! I thought only Americans did that.
I think it's all a conspiracy involving SE, the Illuminati, and Denver International Airport. Sometime after the merger they said that FF would be continuously changing with new innovations in the genre, while DQ would retain more traditional elements, like turn-based combat, and free demos for upcoming FF games as an incentive to purchase them.
I eagerly await purchasing the $35 demo of the next DS FF Game, that just happens to come with DQ IX.