The best way to get tighter feedback loop with developers is to make sure they feel welcome when they bring their input directly on the GitHub repos where the specifications are developed.
As such, W3C Developer Advocates are encouraged to track first-time contributions on the repo they are responsible for, help these contributors formulate their request in a way that is more likely to be approachable the Working Group when needed, possibly redirect them to the right places (e.g. implementation bug tracker) if appropriate.
Another important source of developer feedback can be collected by monitoring GitHub reactions on specific issues and comments, which might serve as a signal of topics that the community feels particularly strongly about.
To help grow the community of developers directly involved in the work, labeling issues as “Good first issue” and “Help wanted” can help guide interested developers.