I don't see why one should code under game maker instead of learning REAL C++, and code for real using a simple media library like SFML...
Well then why dont you go and learn REAL assembly :|...
I understand what you mean about Game Maker, as I use Java and it is a bit depressing to see some kids pulling out a game just like yours with no skills or experience but what you have to realize is that MANY people here a brilliant game designers and focus on making deep, interesting, fun games and do not want to be coders, and want to focus on gameplay.
Game Maker is not killing software because those kids making those stupid little games get washed away and those guys using Game Maker to pump out excellent games would have made a brilliant game no matter what language they used, its just the time frame would be different, they dont want to worry about building a framework, they want to worry about how to make their game fun, and whichever path someone chooses is good for them, dont ride someone just because they dont use REAL C++.
Btw the screenshots look really nice, good luck on your project!