I think terrible is a strong word. Can it be frustrating at the start? Yes I do think they stupidly held very important mechanics like all out defense for way too long. But once you get that ability (commanding whole team to block incoming attacks) the battle system is a lot of fun. I hope they fix this in the remaster, it would be a big mistake not to.
I wanted to like Ni no kuni 2 but I just don't see how only improving the battle system makes it a better game when everything else is worse. Worse visual design, ruin a beautiful game with sinfully ugly chibi designs, unremarkable characters and story. Getting rid of the familiar system (design wise they were no dragon quest monsters but a fun gameplay element no less)
Ni no kuni one came out and resonated with people for a reason. Ni no kuni 2 just came and went.