Good but here's the problem. We just got out of a Dark Age. That means the world you see was sent back technology wise as far back as the Bronze Age in terms of Technological Advancement. Before the Last City was constructed, people were literally back to tribal states that were reminiscent of ancient Greece. The Greeks and Romans were surprisingly advanced for there time but much of those advancements were lost in the onset of the Medieval times of Old England. It wasn't until the Italian Renaissance that anybody took science seriously enough to rediscover everything the Greeks and Romans did. We still can't replicate certain things today at the tech level they were at. That is where we're at now. The weapons you're describing wouldn't look out of place in Destiny's Golden Age. But after the Dark Age, we're lucky there was even enough still left to get back to the level of Advanced Modern Ballistics. We don't even understand our own advancements anymore. That's why the guns are as you see them. The Last City has been at the Space Age level for some time. It's going to take several more centuries before they can build back up to the Golden Age level to produce the kinds of ideas you're giving. Keep in mind the tech level when suggesting this.

Or, the ability to pick up and use enemy weapons after they are killed. Sort of odd we can't do that.

Space Magic!

I stopped reading after "energy crossbows"

Well more energy weapons would be cool. But it can be hard making futuristic weapons without making them generic or played out.

Hmmm