Again, this is a feature, not a bug. If over three-quarters of states or representatives can agree, then an amendment can get passed. If over a quarter of states or representatives don't want to codify something in the constitution, that is not a small minority.
> How exactly are you interpreting that?
I'm not interpreting that portion at all -- I disagree that the founders were only looking out for their own interests, but that's fine to disagree on that bit. I'm responding specifically to "The Constitution never benefited the country as a whole", which is the demonstrably false bit. Every single person in the US today has the benefit of freedom of speech, for instance (despite the fact that historically this was definitely not the case).