Crafting is a big part of the game, but in my personal experience, it's by far the best crafting system I've ever seen in a game before. It's far more flexible than the strict, "Find items X, Y, and Z, and then put them together to make something". Usually, you're required to craft using certain types of items (metals, fruits, types of dirt, etc.), rather than specific items . The items you choose to use, along with the character you use to do the crafting, and the way you use said character's skills all affect the stats of the item you craft.
It encourages experimentation to find out what bonuses you can get. Do you want a healing potion that heals more HP, or a potion that also heals MP, or one that also temporarily raises attack power? This is especially important when crafting gear since you want to have high quality equipment with good bonuses. You're even encouraged to make good use of your alchemy skills so you can craft better alchemy ingredients.
Anyway, that's my take on the game's impressive alchemy system. It feels more like an art than a science, since it's so flexible.