If I'm using off-the-shelf software rather than writing my own, it's because either it's huge and complex or it's not important enough to make time from other projects.

In either case, I'm trading off flexibility for the speed at which I can have _something_ and I care far more about having something that works tolerably well than having something I can change to make it work better. If it breaks, I'll find something else; the software ecosystem is big enough now.

Which is why I'll take "reasonably reliably working" over "I've got the rights to fix it".