I'm not fully on the same page as the OP. But there were 2 other measures listed, beyond the Assault Rifle one.
Is it not a worthy exercise to try to tackle ALL gun problems?
Making the vetting process for gun permits more rigorous, making the process of buying guns more regulated, etc... will not immediately solve the issues you bring up. Which I whole heartedly agree is a larger issue than mass shootings are. But the more we plan, regulate, manage, who ends up with new guns in their possession...eventually, that will have a positive impact on the problems you mention.
Raise the percentage of responsible, knowledgeable, gun owners vs overall gun owners...and you lower the percentage of guns that will get into the hands of bad actors illegally. No? The answer is yes. And if we had started these measures yesterday, we'd be further along in the process today. Every day we just throw our hands up and point our fingers at the "other" people that are causing the problems, is one more day until less illegal guns are in bad peoples hands...AND yes, less Auto/Semi auto, high powered, high capacity guns are available to carry out these mass shootings.