I think you are severely overestimating the negative repercussions of "too many pet projects" existing in the world. If anyone gets left in the cold because they depended on a project that a maintainer gave up on, then that's a valuable lesson that needs to be learned early in one's career.

I argue that, for most small projects, the net educational value of bringing an idea to fruition in public is far greater than any negative externality that such a project imposes. Imagine a world where every side project by a novice engineer is ruthlessly speared to the point of abandonment. I'm sure your counter-argument is that "trial by fire" is the most effective means of growth. You probably believe that forcing people to give up leads them to consider bigger and better things. This is, by far, not the case. Most people give up, and never come back. You are focusing far too much on the immediate value of the project, and completely dismissing its value as a means of creating a motivated, learned individual who can potentially make huge contributions in the future.

Anyway, if your most salient point is "the author should be more explicit about a support plan", then I don't disagree. But man, you could have presented it in a much more accessible and succinct way. If you really care about people taking your advice to heart, you have to be more kind.