Screenshots

Screenshots are not indexed; none of their words enter search. They still affect ranking, because they are the first thing that decides conversion and conversion feeds relevance.

The first two images are the part seen in search results without scrolling. In practice that is where the work ends: the rest are seen only by people who open the page.

If a word is in your title and you still cannot climb, this is most likely where the problem is. rankcusp records tracked apps' images and when they changed; seeing the whole category move the same way is the easiest way to find where to differ.