"The Metamorphosis" is a story about "dehumanization." Can you explain how this is an issue? Is it still an issue? How? What forms does it...

Your question about Kafka's "The Metamorphosis" is a broad question about an extremely ambiguous story. 

If you interpret the story as relating to dehumanization, though, you certainly could perceive Gregor as a victim of dehumanization.  He is turned into a bug, of course.  He is alienated from and mistreated by his family.  He is rejected by his employer.  He is isolated and made to stay in his room.  Dehumanization is prevalent.

The issue is relevant, because dehumanization occurs constantly:  when humans are reduced to facts and figures; when humans are made to give up individuality; when humans are categorized and labeled and stereotyped; when humans are raised or molded according to gender roles; when humans are made to fight wars.

Again, you can certainly make a case that Gregor is metaphorically dehumanized in Kafka's story, and dehumanization is certainly relevant today.