"Google is no longer trying to index the entire web. In fact, it's become extremely selective, refusing to index most content. This isn't about content creators failing to meet some arbitrary standard of quality. Rather, it's a fundamental change in how Google approaches its role as a search engine."

https://www.vincentschmalbach.com/google-now-defaults-to-not-indexing-your-content/

This pretty much confirms my previous assessment:

https://infosec.place/notice/AjnQ7fYpkwNnsgcLLc

@buherator this matches my experience too.
Time to build directories and web-rings again.