There should be a tool that runs in the background of your web browser and, every page you visit, captures and uploads it to some sort of archive. Anonymously,

There should be a tool that runs in the background of your web browser and, every page you visit, captures and uploads it to some sort of archive. Anonymously, and it would have some way to prevent accidentally uploading bank details or other confidential information (this would have to work perfectly by default at least, so the best approach is probably a global whitelist with sites like Reddit, news etc. curated by trusted people). Maybe this tool already exists, maybe it’s what ArchiveTeam uses, but more people should use it. With enough people, you have an archive of websites that people actually visit (well, people who use the tool). With a few people it will only have the most popular sites and outliers, with more people and more time it will start reaching more niche content. Furthermore, sacrifice some anonymity (at minimum you need some identity verification to prevent trivial SEO optimization, you'd probably also want region and other broad characteristics to filter) and you have a search engine. You can scrape the archived sites for keywords; you can determine how popular a site is by how many people visited it; and you can figure out whether two sites are related by the probability that someone who visits site A also visits site B.