Projects like GNOME 3 which have a "vision" are usually the shitty ones, since that vision is usually crap (at least compared to the visions by leading commercial companies, since those have money directly on the line depending on how good their vision turns out to be, while the open source guys are usually just crazy lunatics doing whatever).
On the other hand, Linus Torvalds doesn't enforce any vision for Linux, yet Linux is one of the most successful projects precisely because by not having a vision, it literally does everything and makes everyone happy.
What REALLY matters is:
1. Having an intelligent and capable person maintaining the project
2. Having open policies that only care about technical merits of the work submitted
3. Having lots of developer/company interest and thus a vast community
"We have a coherent vision" is usually shorthand for "We are morons who are too stupid to design truly generic and flexible software, and need a "coherent vision" so that our small brain can cope".