Amazon’s original programming includes some excellent shows, including Man In The High Castle, The Expanse, and The Grand Tour. I found the prime app on my mobile device to be fairly easy to use and navigate, but when I checked the app on a TV using Roku or an Xbox, the problems become apparent. Searching for a show should be more straightforward. If you search by title, it will show you every season separately instead of displaying a single link to the entire show with menus to navigate the seasons from there. The show you are looking for may also be mixed with other shows with similar wording, making the results confusing. Furthermore, navigating throughout a series is not as intuitive as it is with other apps. It can be done, but the interface is clunky.
Prime is a subscription service and comes with thousands of titles to choose from. However, not everything listed is available to watch without an additional charge. These paid titles will show up in searches and as you browse, but it is not obvious until you try to watch some of them that there is an extra charge.
These may seem to be minor things, but some of the issues with the app are not so easy to single out. Looking through comments on several subReddits, Quora, and Amazon customer reviews from its own website, I found similar complaints as these and more, with the consensus being the app is garbage overall.