You look at the changes in society. As many have noted here that fundamentally similarly functioning weapons were available to citizens since at lease immediately after WWII, though today they are lighter weight and easier to customize.
What else has happened?
1.) We stopped institutionalizing dangerously mentally impaired individuals.
2.) In schools we tolerate bad behavior by taking out all forms of discipline until it reaches the level of involving the police.
3.) Explosion of single parent homes - dads not raising their sons, kids being raised by family and not their parents.
4.) In the last decade and accelerated in the last 2 years we have stopped prosecuting a lot of felonies and are turning convicted felons on the street with little or no time served. In other words, we let the bad guys out of prison or never sent them in the first place.
The liberals ignore the massive failure of progressive goals and blame it on the weapon, not the core issues in society, many of which are caused by THEIR own policy preferences.
We may not always get what we want. We may not always get what we need. Just so we don't get what we deserve.