> I've always modeled my team's process on open source development which has successfully produced very high quality "big" software
That's an interesting example and reminds me of an anecdote. At my last company I worked on a very (very) expensive fintech product. We had several competitors including an open source alternative that we were quite nervous about. I wouldn't be surprised if their code quality was higher than ours. But while many customers donated to them, spent a lot of effort integrating them, and talked about them a lot (especially when negotiating contracts) in the end we never lost a customer to the open source alternative.
Don't get me wrong, I love free and open source software and personally use and support several projects. But with a handful of exceptions open source developers seem to be more successful at creating tools for other developers than products for non-technical end-users.