Nobody has more respect for Franklin, Henry, Washington, Jefferson, etc. than I do. But let's get serious here. When these guys were in the prime of their lives, the automobile and the aeroplane were more than 100 years away from being invented, and wars were fought with rifles, cannons, and horses.
As smart as these men all were, I seriously doubt that any of them ever truly conceived of things like ICBMs armed with nuclear warheads capable of going thousands of miles per hour, and biological weapons capable of being transported in a suitcase that could infect and kill thousands or tens of thousands of people. The reality of the world is a lot different today than it was in 1776, and it's foolish to pretend otherwise.
So what you are saying is that like the Constitution is a living document.
I am always amazed when the likes of Ruth Bader Ginsburg are criticized here on FR for considering the Constitution a living document for just the reasons you stated, but when a Republican considers it as such then it's just "reality".
It's not like we don't have a method of amending the constitution if parts of it become antiquated. If we go with the approach that the Constitution just changes with the times then it can mean anything anybody wants it to mean.