I disagree. The gambits are a unique and interesting way to build complex AI that works much better than your average party AI in an RPG (especially games like Ni no Kuni), but the game never "plays itself", and most significant fights (hunts and bosses) require you to still make a bunch of decisions on the fly, because the gambits really can only do so much, and are much more suited to a decision you'll always make (like, enemy weak to fire -> use fire-element spells).
What the gambits did do, IMO, is highlight just how silly random (and for these purposes, random means the unimportant fights) encounters are in RPGs. You could throw together a gambit system for, I'd say, 90% of JRPGs, and it'd be perfectly functional for most fights. To me, that right there shows you how intellectually and developmentally lazy these kinds of fights are, and I'd love to see more games say "You know what, let's just excise this element from the game entirely."