How exactly do you think an open source software project should be managed? People are going to have disagreements about changes, and there needs to be some method of adjudicating those disagreements. Democracy is near-impossible in those circumstances because key problems like suffrage (who counts as enough of a contributor to have a vote?) are hard to fix, and because actual technical expertise is important to decision-making. Wikipedia is probably the best example of a project that's run democratically, by consensus at least, and the net result is that more effort is wasted on politicking than actually writing content. The only reason this even works for Wikipedia is because there's no shortage of people who can write and copyedit encyclopedia articles. Programmers are more scarce, and more allergic to politics.

So benevolent dictatorship it is, plus the freedom to fork. As for Rails, changes like using jQuery instead of Prototype (pre-3.1), or using HAML or something like that doesn't actually require making any code changes. In fact, these controversies are classic bikeshed arguments. It's not a serious criticism of Rails that the default gemfile doesn't include a gem you prefer, because you can change the gemfile yourself. It would be a serious criticism of Rails--and, indeed, a reason to fork--if, for instance, there was strong disagreement with how Arel is implemented. But there's 100x more Rails developers with an opinion over HAML vs ERB than there are Rails developers with the slightest clue about how to implement Arel.