I've long been interested in Active vs Passive hobbies, why one is better than the others, and so on. Here's a nice reddit post that captures a similar mindset around gaming. So reading Flow gave a lot of clarity to these ideas.

Any programmer who's been 'in the zone' and loses sense of time knows the feeling of 'Flow' and that is the subject of this book -- Deep hobbies that improve one's self.

The author categorizes activities with good 'flow' if they meet these criteria:

Here are some sections from the book that caught my attention:

"The wisdom of the mystics, of the Sufi, of the great yogis, or of the Zen masters might have been excellent in their own time -- and might still be the best, if we lived in those times and in those cultures. But when transplanted to contemporary California those systems lose quite a bit of their original power. They contain elements that are specific to their original contexts, and when these accidental components are not distinguished from what is essential, the path to freedom gets overgrown by brambles of meaningless mumbo-jumbo. Ritual form wins over substance, and the seeker is back where he started."

"Pleasure is an important component of the quality of life, but by itself it does not bring happiness. Sleep, rest, food, and sex provide restorative homeostatic experiences that return consciousness to order after the needs of the body intrude and cause psychic entropy to occur. But they do not produce psychological growth. They do not add complexity to the self. Pleasure helps to maintain order, but by itself cannot create new order in consciousness."

"In today's world we have come to neglect the habit of writing because so many other media of communication have taken its place. Telephones and tape recorders, computers and fax machines are more efficient in conveying news. If the only point of writing were to transmit information, then it would deserve to become obsolete. But the point of writing is to create information, not simply to pass it along."

The middle quote is a satisfactory answer to my question on what differentiates mindless passive hobbies from effort-intensive active ones: the latter create better versions of ourselves.