Cody, the key is that the engineer has to
do for one dollar, not
fail to do or
poorly do for one dollar. I've had to redesign and/or repair poorly made products myself. I have the piece of paper that says I graduated with an engineering degree, but the paper itself is meaningless except when applying for a job, so mine's shoved away in a drawer somewhere.
In most manufacturing environments, the engineering department has engineers and designers who develop and test products. Then they are handed over to the manufacturing department, where the design is altered to save cost, simplify, make easier to build, etc.. Sometimes changes are made without consulting the people who did the original design, and without the benefit of understanding why that original design was done the way is was, things can go very badly.
Then there's the fact that every profession has competent folks and incompetent folks. The point I was trying to make with the quote about doing for one dollar what anyone can do for two or three was similar to what you said in the last part of your post. Machining a fuel tank from a solid piece of aluminum isn't my idea of good engineering. But then not everything has to be, I guess.

From what I've seen of things you've built, you don't fall into the "any damn fool" category anyway, so I'm not sure why you said you do.