Its interesting too look at the WP project itself in this regard. It(they?) have improved greatly over the years. Before things were hidden away att hallway discussions in WordCamps, or barbeque parties, some things probably still is, but overall things are much more transparent and inclusive nowadays. Now with the make blogs, slack and being easily able to link to discussions etc things are only going to get better. Given the long time period things are decided and separate projects being made such as the REST API and Fields API etc there is risk of things getting too spread out again but so far everything is relatively easy to trace. One improvement would be if there was a log of all the meetings with a link back to slack. That would be a great addition I think.