The overall theme of the story is a soldier returning from war and having trouble going back to "normal" life after having gone through the traumas of battle. Krebs finds that the people around him have no concept of what he has gone through, cannot comprehend it even if he were to share it, and he must lie and pretend to be normal in order to fit back into the town he used to call "home." Each of these challenges that Krebs faces are challenges that soldiers returning from battle have always and will always face.
If we look at American society today, we are still deploying troops to the Middle East to help train and fight. Since 2001, we have fought in two separate wars, in Afghanistan and in Iraq, deploying more than 2 million troops. The soldiers who have come home from these wars have faced the same challenges as Krebs, and although Krebs was probably suffering from Post Traumatic Stress Disorder (PTSD), that was not a term or diagnosis following World War I. Now we recognize this as a disorder that requires help from mental health professionals and understand it as an epidemic among returning troops. Their readjustment to home life often takes a very long time and is incredibly difficult, for all of the reasons we see in the story.
Many "return with varied complex health conditions and find that readjusting to life at home, reconnecting with family, finding work, or returning to school is an ongoing struggle" (National Academies).
Hemingway's story is actually timeless because war has always and will always continue to take an emotional and physical toll on soldiers that, in many ways, only other soldiers can fully understand.