Well, no. It would be a good idea to remain beholden to the philosophies that still ring true today, but it makes no sense to be stuck with something we don't agree with if we want to change it through the amendment process. Otherwise, there's no point of an amendment process.
You mentioned banning slavery. I would argue that it is inconsistent with the principles of the original Constitution. Not because the founders weren't democratic and wouldn't have supported ending slavery (even slaveholding framers, for the most part, thought the institution was embarrassing and wished it would end), but because the amendment dramatically shifted the balance of federal and state power. Section 2 of the 13th Amendment, along with Section 5 of the 14th Amendment (and one of the sections of the 15th Amendment I'd have to look up) say "Congress shall have the power to enforce this." The amendment was designed to dramatically expand federal power in a way the founders wouldn't have supported. And this makes sense. If they supported it, they would have put it in the damn constitution.
In short, we have a written constitution to constrain our actions in order to ensure conformity to the rule of law in a way that the founders intended and we have an amendment process so a consensus of America can change parts that we feel should no longer be applicable to us.