Since the inception of MIDI files, many composers have used them, but the question how effective they are.
Welcome to the Magix user to user forums.
Unfortunately it is impossible to really answer your question!
The effectiveness of the use of MIDI files and packs is entirely dependent on what the user wishes to do with them , which program they wish to use them in and whether that program includes the same "Sound Generators" (e.g., VSTis) as the "composer" used.
I suspect many users will see them as a good and valid "starting point", nothing more. They can be used as "examples" or "building blocks" but are unlikely to be 100% suitable for a particular project without some human "editing" or similar intervention.
There may also be a question of copyright, if the user chooses to employ one of these packs or files in their work without making any changes to the originals.
(Just my opinion).
Jeff
Forum Moderator