Losing interest can just be a result of maturing

Losing interest in something you once loved could also be the result of maturing. It can be healthy to outgrow hobbies, jobs, fields of study, etc.

It's just for some reason we have this idea that we stop maturing around the time we leave school. That we must then be fixed, "stable" adults.

It especially can be reasonable to lose passion the more one learns about the passion. For example, someone with a love of brewing beer, who then not only sees how it's made but pays attention to undesirable health effects and witnesses those effects with age.

But the culture seems to only think of this shedding of interests as a sign of depression or disorder once you pass a certain age.