I don't think that's true. I've long worked with software both proprietary and not, and I find myself digging deep all the time. I shouldn't have to reverse engineer my dependencies to find out why they're broken. When I do figure it out, I should be able to send a patch so everyone benefits. Without these basic things in place, I simply cannot get work done.

The other advantages are not really important. If an open source offering is lacking something, I can just add it myself. If the proprietary version is lacking something, I cannot.