Ryan compared those words to what Chronus said earlier: "You might change the future a little bit with the knowledge and the power you just obtained, but in the end, you will only prevent your deaths for a few minutes. You can say that the future isn't set in stone, but big events are a culmination of uncountable small events. Once those take place, it is impossible to prevent the result."
It made sense. Those primordial creatures had the power to make many things happen. Maybe sooner or later, mana truly would return to Earth, and humans would have to face those problems without the help of the features created by Merlin. Without his rank and classes system, humans would never obtain the power to fight back so fast, nor would they be able to create domains that could protect thousands of survivors.
