You are exactly right in your reasoning -- fewer guns won't solve the crime issue because at this point, it's practically impossible, and second, eliminating guns doesn't resolve the underlying issue of violence in America.
When you eliminate a nation's core virtues and impose an amoral society, violence is just an inevitability. We really didn't have school shootings prior to the 1990s, which sadly isn't surprising. In prior eras, children respected their parents, and we largely followed common decency.
Not anymore.
RE: Miami shooting and my take on it.