I prefer the adjectives strong/weak over good/bad or better/worse to describe developer skill for two reasons. Good or bad can be perceived as an inherent quality, while it is obvious that strength is acquired. The second reason is because better/worse can imply subjectivity. That is, that it wouldn't be possible to tell a strong developer from a weak one because it is all in the eyes of the beholder or some BS like that.

Onto your question, the answer is yes, very much yes. Solving puzzles indeed makes you stronger. It exercises your brain exactly like lifting weights exercises your muscles. Almost any skill can be trained the same way; there are chess puzzles, writing "puzzles", acting "puzzles", even musicians have certain "puzzles" they hone their techniques on (e.g Segovia scales).

I don't know why puzzles have such a bad rep on Hacker News. It may be a case of sour grapes. Like you see a jacked dude and you think "Eh, easy with steroids!" or "Yeah, but does he know basic arithmetic?" Cause admitting that he spent countless hours in the gym while you (like me) spent countless hours watching movies and eating chocolate is a too big of a blow to your confidence.

Apparently some dude didn't land a job with Google because he couldn't invert a binary tree. So he thought it was useless. I looked it up (https://leetcode.com/problems/invert-binary-tree/) and had a laugh. Because the solution was readily obvious and required no more than three lines of Python.