Those who do not learn history are doomed to repeat it. Why do the Big Bads of Star Wars keep building these huge, planet-destroying weapons? From the original Death Star, to the not-quite-completed one in Return of the Jedi, and The Force Awakens' Starkiller Base, they've kept doing essentially the same thing, and had the same disastrous results. So, they can't build ANOTHER Death Star, can they? Well, of course they can, because really, if you've got something that can destroy entire planets, what other weapon is going to top that? Sure, it has a few flaws, but if you could actually perfect it, then it'd be the greatest weapon in the galaxy. They may decide that it's too ridiculous to have yet another of these weapons, and it'd be justified, but don't put it past the logic of The First Order to think they can do Starkiller Base bigger and better.