The Sharp LR359021 CPU is what you're conquering which is an 8080 CPU with a few throw-ins from the Z80. There are enough tools to write a GB game but perhaps there aren't enough good samples or a library (mini engine).

But in general I agree that the biggest problem with making retro games is getting a comfortable dev environment that just works. I think this is the motivation behind some of the 'simple' NES development environments that have been coming out.

I feel like a really good IDE / debugger and well documented library for the Gameboy + samples would go a long way.