There seems to be a common misconception that a site will rank well on search engines, or not rank well or search engines, but that isn't how search works.
Search engines attempt to return the best possible results for the search query entered, so each page on your site is considered separately and judged on its relevance to a particular query. You might have a site about pets, and find your page about tortoises ranks very highly. On the other hand, your page about dogs doesn't do nearly as well. That might be because the content is less good, or because there are a lot more sites competing with yours. The point is, search engines consider each page separately, so you need to do the same. Yes, they will take into account the overall quality and content of the site, but that's only one factor in ranking.
You might find this video helpul: