I mostly agree with you, but also don't want to be too developer-centric. Sometimes the ideas come from people who aren't primarily developers - production engineers, system architects, etc. Let's say an idea from such a person is fundamentally good and will benefit the project but they lack the time or skill to do more than prototype it. What should happen?
(a) Drop it on the floor.
(b) Let their patch(es) languish and eventually get reaped. Same result in terms of functionality, plus contributes to an "maintainers aren't open to new ideas" reputation which harms recruitment/retention.
(c) Get a developer with more knowledge/skill to finish it. In general, this is just going to be the maintainer, because nobody else will have a strong enough sense of ownership to sacrifice time toward their own goals for it.
Obviously this is going to be case by case, but I'd say that (c) is at least sometimes a valid answer. Depending on the makeup of people involved with the project, which in turn might depend on the nature of the project itself, it might even be quite often.
