Mastering in Garageband

Before you export your garageband track try some basic mastering. I discovered the genre-based presets are still there and that may be all you need. Click on master and output on the mastering window at the bottom of the interface. If you then click on the settings up/down arrows you can see 06 mastering. From there you can choose a final mix preset that will really beef-up your track. This article is quite helpful;

https://producersociety.com/how-to-master-a-song-in-garageband/

Real annoying song example and delivery is a bit tedious but this is the most solid video on mastering in the current garageband I could find.