Years ago it may have been easy to get listed and lots of visitors from the search engines. You just created a site with several pages of unique content. Then copied those pages onto many domains. Pronto! Dozens of Web sites. Each site would then be individually listed in the search engines against the relevant keywords. That was great for the early affiliate ads.
Then the impact of Adsense that spawned development of various software and scripts to create an endless stream of simple Adsense sites. With a few appropriate keywords fed in instant Adsense keyword theme pages were created. Some people use 1000’s of these keyword theme Adsense pages on hundreds of domains. They all get indexed and they all got visitors. It was that simple though unfortunately, these tricks do not work anymore.
The search engines are way smarter now. They can rapidly compare content from one source to the next. If your pages look too much like already indexed pages, you will probably be on the last page with no visitors and no Adsense revenue.
There was also software like doorway page creators, niche portal builders, and such that all fail the Google test. While not...