And? Then change it then. If the 2nd Amendment is still there and not repealed then it's a moot argument. Stop trying to whittle more and more of the right guaranteed by the 2nd by couching it in "common sense" bullshit.
And when it was written militaries where standing in lines firing round shot out of inaccurate tubes en-masse hoping that they might hit something. A single person with a modern SAW could have taken out an entire company unaided. You're suggesting that there should be no adjustment based on changes to society and technology because it's written on a specific piece of paper.
Grapeshot. Pickleguns. There were many advancements in weaponry during the lives of the founding fathers but I don't remember them writing all about how they were wrong because weapons are too dangerous for mere mortal civilians to own.