I think you’re forgetting the most expensive commodity that players have… time.
Not all players have an equal amount of it. Players need to see that the time investment that they do get to play, is spent doing, at least in some part, the thing that they enjoy the most about the game. Spending coin is a way to do that, so whilst in some part I do agree that you technically don’t need any coin to build, when you factor it against available time to play, and actually spend doing an aspect of the game you enjoy, then I say it’s an absolute must.
Well, it kind of does… players can compete to be the leader of a settlement, and of the whole planet. It’s an intrinsic part of the game - it’s a part that some players enjoy, beyond the other professions/play styles.
If creativity is the same as art… I’ve definitely mentioned both art and income in the same post 
The fundamental difference here, is that building produces no by-product that can be sold. Both hunting and mining, by their very nature, create a usable resource that can either be used by that player to create something else, or be transported anywhere in the universe and sold to another player. Building does not have that same transportability… it’s a service, not a product.
I do like the idea of blueprints as well… I’m just worried that they’re not a viable, sustainable source of income to a building focused player.
…and it’s really not about “a money game”… it’s about creating equal opportunity for each play style to be able to earn coin (seeing as we already earn XP from all of these things) from what they enjoy doing … even if some - and I won’t speculate on what percentage of the player base that is - don’t want or need coin.
Curiously though… quite a lot of builders jumped at the chance to enter this…