Taken at face value, then yes, obviously more people looking at a specific piece of code will make it better. But this does not extend to the entire landscape of open source. Most developers, especially ones doing so as a hobby, would much rather work on their own new code. Not look at someone else's old boring code. We would rather reinvent the wheel a thousand times before touching a line of code written by someone else.

This becomes even more dire when you look at code no one wants to touch. Like TLS. There were the Heartbleed and goto fail bugs which existed for, IIRC, a few years before they were discovered. Not surprising, because TLS code is generally some of the worst code on the planet to stare at all day.