I’m working with GAS in my commercial project and it is really powerful, the only reason to avoid using GAS - is you don’t need to have a rich ability system because GAS needs C++ implementation, and also it is might be overcomplicated for simpler games.
In my pet project, I know that I don’t need a lot of abilities with a lot of effects, so that’s why I’m not going to use GAS, it will add a lot of effort for nothing.