I think this is a prime case for individual outreach.
"Hey I saw you on Indie Hackers building X. I am building in public, too.
I just finished a site that helps small projects raise funds and get feedback. Think producthunt for indie hackers. It's free to sign up and I am going to do a big marketing push in the next few weeks. Would love to have your project on there!"
I totally agree, I don't think Indiebackers should replace that process, it's completely different.
I'm terrible at networking but I hope this launch will get me out of my comfort zone.
"Hey I saw you on Indie Hackers building X. I am building in public, too.
I just finished a site that helps small projects raise funds and get feedback. Think producthunt for indie hackers. It's free to sign up and I am going to do a big marketing push in the next few weeks. Would love to have your project on there!"