Regarding a "feedback campaign" - I feel it attracts spam and fake reviews...
Yes, that's the issue.
Something more sustainable would be a membership module that tracks activity on your site, and the activity can be whatever you want it to be. Comments on existing casinos, operator review requests on a bullet-board or just plain website feedback. The better the activity of a certain user is, the more do they get from the membership. Maybe a point system with rewards or something, but now we're entering extra dev work + building a community around the brand is always a hard thing to do.