It's not exactly about about the turn-based per se in my opinion, but, in fact, it's about changing the core gameplay of a series. I mean, FF XV just looks like a Kingdom Hearts/Dissidia game. FF XII, for example, while changing the gameplay of the FF series, was still a turn-based game in the end. FF XV looks like an action game, which is the direction SE has been pushing the series since FF VII, but the truth is that most people would prefer a new series being created with that kind of gameplay instead of changing a series known for it's turn-based gameplay approach.