That exactly is the reason to call for the ban of certain weapons and accessories. It's not that they are more deadly, it is just by popularity. In Germany Balisong are banned. They are among the least useful knifes in a fight - but they are cool. I guess the AR 15 is among the most popular for mass shooters. Ban it or restrict it's use to people who really need it.
But beware....banning the AR15 would achieve nothing.
There are many alternatives, some with more firepower.
But urging a ban that isn't constitutional, or doomed to
be useless (eg, the 1994 ban) is counter-productive.
It gives the appearance of progress, which saps the will
to do something actually useful.
Instead of banning, I sense too little desire to restrict
who possesses guns, training required, & storage being
secure. Such events seem to cause partisans to dig in
to extreme positions.