In the weekly Fedora program update that I publish on communityblog.fedoraproject.org, I have started to include a count of the open package review requests. As of this moment, there are ~1300 open review requests. Some of these were opened in 2006.
Have a look at https://mattia.fedorapeople.org/review_stats/
These pages were generated by the script at https://pagure.io/Fedora-Infra/review_stats which should replace (?) the actual script that generates https://fedoraproject.org/PackageReviewStatus/
In general, both the old and new pages can give you a hint of why
a review ticket is stuck. The newer script hides less tickets than