Oh, that’s just not true. Buy a cookbook or two. It’s not hard to bake a decent cake from ingredients unless you’re grossly incompetent in the kitchen.

The exotic ingredients are often there either because a normal ingredient would spoil or can't be powdered. Fats, for example, are a major part of some baking and those cannot be dried out and will go rancid in a box.

It can seem intimidating until you realize that an egg, a pat of butter, or milk are just mishmashes of compounds not always easily added in mass production. (Yes, you can powder milk and eggs, in some baking it's just fine in other it messes with the flavor).