GarageBand was first introduced as a part of Apple's iLife suite, aimed at providing a user-friendly music production environment for beginners and hobbyists. Over the years, it has evolved significantly, incorporating features that were once considered professional-grade. The software's interface, initially simplistic, has become more sophisticated, offering a range of instruments, effects, and editing tools that cater to both novice musicians and seasoned producers.
You can still download an older compatible version: Apple allows users to download the last compatible version of an app. Sign in to the Mac App Store with your Apple ID, click “Get,” and a popup will say: “Download an older version of GarageBand?” — confirm, and you’ll get GarageBand 10.3.5 (works on Catalina).