Why does God make us find our own cures for diseases, instead of answering our prayers with the cure?

Because the Realization of the One True Way has yet to be realized. It's too late to obtain the 8th chronicle, but once the Order of the One True Way's archivists reclaim the 9th chronicle from Sieg's Le Mignon Company in Castle La Bakery, the One King will present himself to the world and unite all the worlds within the Infinity. Only then will all these questions be answered, for that is the Order of the One True Way.