Thank you for the PolySci 101 lesson, but citing the text doesn't prove your point.  
Here are views, left and right, on the outdatedness of the Constitution.
http://www.hoover.org/research/our-outdated-constitution
https://forwardprogressives.com/a-reality-many-americans-dont-want-to-admit-our-constitution-is-outdated-and-broken/

I personally think the Founders didn't foresee the idea of the "career politician".  I think they expected an elected official would do what was sensible for the country or their region they represented and then get back to their regular lives. Heck, who would want to be a politician when you could be home farming?  The politician who's first focus is 1) keeping their current post, and 2) alinging themselves for the next gig is a significant deadweight in the system.

My upper division PolySci courses talked about a concept of the "broken spring of government", I think that is now quite evident in our modern situation.