I think the lack of firearms is a non issue in the game personally:
For one, the dinosaurs in the game are expensive. So strategically speaking are you really going to pull out the big guns on your 3+ million dollar star attraction? To quote Masrani - "we have 35 million invested in that asset, we can't just kill it"
For two, don't you think it makes things a bit more on edge and suspensful/urgent if a dinosaur breaks out and you can only take care of things non leathally? Not only do you have to act fast, but you also need to hit multiple shots and wait for it to take effect. That to me is far more intense an experience when you're under pressure than just shooting a dino in the head for a kill
It also goes without saying that Frontier knew exactly what deadline they were on when they took the project on, considering they were working closely with Universal to coincide with the release of a film that was already over a year into production. Universal didn't rush Frontier, they gave them a deadline. Frontier accepted that.
As you said though, and as we've all speculated for a while there will be free DLC after fallen kingdoms release (which may well include updates and fixes outside of dinosaurs) and no doubt there will be some form of regular free dlc alongside paid dlc to address issues, add content and improve core mechanics, just as they've done with planet coaster