Are wasteful when a smaller weapon can do the same job. Massive battleships are wasteful when the world is going to air power. I know that, but I also know the "bigger is better" mindset, and the national prestige angle. They also just invite someone to make something with larger guns or thicker armor to withstand the new weapons.
In the end, we'll see if this ship gets made, or will be replace with large amounts of cruisers, or case off 14 inch gun armed battleships from retired American ships.
-----------------------------------------------------------------------
It will depend on if the 17 inch/ 45 caliber is superior to the currently avalible 15 inch weapons at the time, and or the probability of actually constructing those weapons. The 16 inch 50 cal Mark VII should be superior to any Chilean 17 inch cannon, but, 16 inch guns are illegal, at this point in time, to treaty nations...which is of course another reason for Chile to have to do this herself, but thinking the older 16 inch won't be much better if better at all then the modern 15 inch cannons.