As the maintainer of an an alternately alive/not-really-alive github-based project, a problem with changes being voted in is that many submitted PRs are of fairly low quality.
Just because an idea is needed by the consumers of a project doesn't mean that any given implementation will be satisfactory. Many voters will tend to be uncritical and/or have different standards. E.g. did the submitted change include tests? Did it pass existing tests? Did it implement a feature that was actually needed (e.g. did it solve a "docs" bug via a "code" patch)? Bikeshedding over existing functionality? The list goes on.
I'll also note that GitHub's great CI integration support (used by Travis CI, the Jenkins GitHub plugin, etc.) can significantly aid the proposals in TFA. E.g. a PR that doesn't pass CI would automatically be ineligible for merging.
Just because an idea is needed by the consumers of a project doesn't mean that any given implementation will be satisfactory. Many voters will tend to be uncritical and/or have different standards. E.g. did the submitted change include tests? Did it pass existing tests? Did it implement a feature that was actually needed (e.g. did it solve a "docs" bug via a "code" patch)? Bikeshedding over existing functionality? The list goes on.
I'll also note that GitHub's great CI integration support (used by Travis CI, the Jenkins GitHub plugin, etc.) can significantly aid the proposals in TFA. E.g. a PR that doesn't pass CI would automatically be ineligible for merging.