I think the title is misleading, since the writer is just talking about how passive income can lead to depression. Passive income isn't bad, and it doesn't mean everyone goes into depression because they have no purpose on what to do.
I for one, won't ever get bored with life, since life is like a sandpit with many things to do. I may hate it at times, but that's because I have "psychological uniqueness" lol... it's not because life is so hard.
If a day job gives you purpose, why quit it? Just keep doing it even if you are a multi millionaire.