Define GarageBand as an entry-level but powerful DAW. Introduce version 10.4.8 and address the premise that software versioning is less critical to sound quality than proper user technique.
When exporting, you will see a checkbox for "Normalize." Normalization analyzes the loudest peak and raises the entire song. This artificially reduces your bit depth (effectively turning your 24-bit recording into a 16-bit recording by raising the noise floor). Control your volume with limiters, not normalization.