unity and some other engines provide a much more modern design approach, beside better marketing, faster development, and supports more operating systems. its free version has a different feature set from gamestudio, but enough for a lot of games.

gamestudio is fine for game development, especially if you are a beginner (imo the easiest engine to start with), but only for pc, and still using directx9. moreover, you have to create your own tools for more complex games as the incuded ones are quite old, and imo need commercial licence supporting shaders for an acceptable quality.

I don't think gamestudio can be studied in any school, but maybe I'm wrong...

yes, but much less than unity, thus much more difficult to find a job.