Like many health issues (mental or otherwise), its a matter of degree.

Everyone can relate to the experience of lacking the focus to perform an un-stimulating task, and to the experience of procrastination - and so that often leads to the kind of blasé reaction you offer here (no offense). This is a very harmful kind of attitude.

Everyone can relate to the feeling of being sad too - that doesn't mean we're all suffering from depression. Most people can relate to the experience of drinking too much. But they aren't all alcoholics.

It's when the degree of such behaviors/states-of-mind become so prevalent and unshakable as to be destructive and harmful in a person's life, that they become disorders.

This is 100% true. A functioning and reasonably healthy person can exhibit or be affected by anything in the DSM5 - from hearing voices (God) to alcohol consumption (social lube) to compulsiveness (hard working).

It's only when that person can no longer function in a healthy way that it becomes a mental disorder.

And for many of us we slip in and out of it.

Even activities that are risky, drinking or skydiving, can be a part of a healthy and functional person.

And everyone anecdotes about how they "beat" that by doing some random activity, life is long. Keep beating it, but don't judge those that are affected by it. Just wait a decade and you very well may be the same situation. Life is all about kindness, however you can be kind, do it.