There's your first problem. Our "gun culture" isn't committing mass shootings now any more than they did then and the same exact technology was available. Some very few mentally disturbed people & people committed to ideologies which excuse mass violence are committing these crimes. Conflating them is a logic error.

Now, 40-50 years ago, before we had purchase restrictions mind you, what tools did we have available for dealing with the severely mentally ill that we don't have (or don't use) today?

For good or ill, what tools & law enforcement mentality did we have available to track known centers of violence w/o fears of being called prejudiced, causing us to ignore warning signs (such as those we always see were ignored for PC reasons after these attacks)?

Blaming the guns, which have not changed, & law-abiding gun owners, who are also the same kind of people, for the actions of an incredibly small minority (mere hundreds of people over decades in a pop of 330 million) is puerile.