I disagree that the framers delegated to future generations the meaning of vague terms, like due process, equal protection, etc. Those words were not plucked out of thin air, but had core meanings that were understood at the time of the framing (although I grant that there is certainly ambiguity outside of the core). The goal of judging in constitutional adjudication should be to attempt to discern those original understandings and apply their concepts to present-day situations. For example, it is lunacy to interpret the "cruel and unusual punishment" clause to proscribe the death penalty because we may now consider the death penalty to be cruel and unusual, considering that the death penalty was applied at the time of the founding.
As for your last paragraph, one of the many attributes of originalism is that it seeks to keep the balance of governmental power versus the power of the people the same as it was at the time the constitution/14th amendment were adopted. In an orginalist world, if the people think social values have changed, the people can freely enact laws that reflect those changed values. Nothing in originalism, for example, keeps the populace from authorizing same sex marriage, if that's the way the political winds are blowing. The "living constitution" takes that power from the people and gives it to unelected judges, at the aggrandizement of the judiciary and to the detriment of the people. In other words, it has nothing do with politics, and everything do with the proper role of the judiciary. As an originalist, I happen to believe that we shouldn't be governed by what 5 Ivy League educated lawyers think "due process" means for them. I think it should mean what it meant at the time of the founding/adoption of the 14th amendment, and all the rest is given to the people to decide.