Marcus' contrast before and after meeting Thomas is thought-provoking. I thought Marcus was a child who didn't care about anything. But this is actually just numbness after a long boring life. In addition, although it is not easy to understand Marcus' mother, the way she treats Marcus is still debatable.
Marcus doesn't want to take medicine. Her response is threats and intimidation.
Thomas, on the other hand, asked Marcus to do what he had to do in an empathetic way. This contrast shows that children (especially adolescent children) should be treated in an equal and respectful way, not by coercion.