You can think of GarageBand as a simplified version of Logic which is used by a lot of professional producers, so GarageBand is maybe not as amateur as it might seem. More of a simplified entry point into music production to get people eventually into Logic when they get more advanced. Ableton includes a lot of more professional features, but if you want a more serious comparison I might compare Ableton to Logic where you can basically accomplish the same things in each one with different workflows etc.