The point about gangs is that it's OBVIOUS that guns don't keep you safe.
The Founders were not ignorant to technology. They were well read on history, military and civil. The were inventors, statesman, scientist and educated. In the time before the Colonies revolted, there were muskets rifles with revolving barrels being worked with. They were not practical until the advent on the percussion cap, and even then not reliable. The firearm had progressed from bamboo tubes to naval cannons. An example of foresight is Ben Franklin discussing the mobilization of soldiers from the sky.
To say they could not foresee the advances of firearm technology is unlikely.
Self defense is a natural right, not a manufactured right. The use of firearms were considered an extension of that right.
The various Militia Acts of the time did require firearm ownership. Exemptions were to groups such as the Quakers. They were not always enforced, there was more common sense in that time.
The issue of registration has a history of leading to confiscation, that is the reason it is opposed.
Gang wars? That is a ridiculous comparison to the responsible ownership of firearms.