The event could have detailed emergency evacuation routes

I like this idea. More blatantly obvious mass exodus routes. Seems like at so many of the venues they're so concerned about keeping people out that they Fort Knox the things. "In case of emergency break glass" but fencing that only opens outward or something. And obvious signage.

created shelter in place areas

Another good idea but logistically impossible to create that for these outdoor festivals that bring in 20,000+ people and set up in open lots. And what does that look like for rapid fire coming from 32 floors in the air?

and made sure every concert goer received instructions on what to do in the event of a terrorist attack.

Easy to do. Include this info with every ticket purchased. Making it available is one thing. Getting people to actually read it is another. Maybe make it a screen that people have to agree to before they're able to complete their online purchase and then also in the confirmation email.

Acknowledging that things like this are going to happen and beating our head into the gun control issue has gotten us nowhere for the last 20 years.

I disagree. We shouldn't live in a society where we have to "acknowledge" that these things just happen. Mass murder rampages shouldn't "just happen so get used to it." The gun control issue has gotten nowhere because radical ideologies have continually pushed for greater and greater access and used their extreme lobbying capabilities and money to pigeon hole politicians. "You're either for us or we're going to back someone else who is." Gun control, as with most of the politics in America, has evolved so much that there is seemingly no gray area with it. You're either for guns or not for guns, and if you're view is against mine then fuck you. "Oh this open carry 9mm scares you, well good, you'd shit your fucking pants if you saw what I've got stockpiled in my house! You pussies."

For fucks sake, people are electing politicians who flash their guns at rallies and the President has called for people to assassinate political appointees from the other party.

“If she gets to pick her judges, nothing you can do, folks,” Mr. Trump said, as the crowd began to boo. He quickly added: “Although the Second Amendment people — maybe there is, I don’t know.”

America has turned into a competition. There's no middle ground. There's only one side wins and one side loses. And the side that wins pushes the extremes further and further out to protect themselves.