This is exactly right. However, something that I've found frustrating is that in many projects (at least the ones that I'm interested in), it feels like there's a secret roadmap that's not documented anywhere outside of the maintainer's head(s). You can scour the wiki, watch the IRC channel and mailing lists, and read through the issue discussions, and you still won't have a good sense of what they want done next or if the change you want to make is incompatible with some big planned rewrite. I know the answer is to just ask—and I've done that more and more recently—but that can be a big hurdle if you're just getting started.
I'm trying to build a community for a project right now, and this is something I'm very aware of. I'm trying to report on what I'm working on and planning in the project chat so that if someone else comes along, hopefully they'll (a) understand the current status and (b) feel comfortable asking about the overall vision.