Apple intended for both apps to be replaced by Photos, but some users prefer to use the older tools instead of moving on. In the case of Aperture, Apple's discontinued professional photography tool, it was effectively discontinued five years ago, but the app only stopped working in Catalina, while iPhoto provided a more consumer-friendly and simpler photo management system until it too failed to operate in Catalina. Arguably the biggest casualty is iTunes, which was eliminated in favor of separate apps for Apple Music, Podcasts, and Apple TV, while the Finder handles iPhone and iPad backups. The release of macOS 10.15 Catalina brought with it a number of changes that affected how apps functioned, including tools Apple itself produced. But, there is a solution with the Retroactive app. Aperture and iPhoto don't work in macOS 10.15 Catalina, and iTunes has been completely replaced.
