Been troubleshooting this decline for months. About 6 months ago, before I started paying attention, AppGoblin had no meta headers, no canonical pages, and no SEO optimization of any kind. Many pages routinely took 10 seconds to load.
At some point I took an interest in growing the site, it honestly only gets a few users a day at most, but I enjoy working on it and think it’s interesting. I added it to Google Search Console and started trying to get the SEO ‘best practices’ started. This somehow led to a steady decline to the point where nearly the entire site has been deindexed from Google.
Google also refuses to crawl AppGoblin’s sitemap (despite Bing and Yandex having no issues).
It’s quite ironic that the site seemed to do better before I started following SEO best practices (Header meta tags, keywords, descriptions, faster loading pages, and adding page to Google Search Console). Of course, since it’s a fun hobby site, I’ll just keep plugging away at the problem, so hopefully one day I’ll figure out what the Google issue is.