The main advantage of open source for me isn't that all bugs are found. It's that when I encounter a bug I can check the code, report it, fix it in my fork and get it fixed in the main repo eventually.
With closed source you have to make do with workarounds.
There was a point a few years ago that GTK+ dev was complaining that only he was left to work on the project. A single person for a whole GUI lib..
And GTK+ is the basis of so many FOSS it's not even funny...