Hi Francis! This looks like a really cool product idea. I think there's a ton of value for job-hunters (both passive and active), but probably little value for recruiters. So, what if you didn't worry about the recruiters? What if you built integrations around all the recruiting messages engineers get. They could have a central repository for managing their active search and archiving messages when they are more passive.

I don't think you should scrap the project or even drill down to a more specific niche. I think you should simply focus all your efforts on catering to the job hunter and that means finding a way to not worry about the recruiters.