The hostile responses you've go this do rather demonstrate your point. Building peace in a world bristling with nukes held by independent sovereignties with limited information about each other and often incongruent self-defined 'interests', is indeed a hard problem. Hard problems require work and thought and research to try to solve. If conditions change to make the problem harder, more resources and work are required.
That readers here find that requirement incomprehensible for this specific hard problem is exactly the point. Peacebuilding (as an activity, an actual diplomatic project, not a hope) has indeed fallen out of vogue and out of the collective political imagination. Little being permanent in international relations, it could yet return.