I picked Driller initially and stuck with it. Progression felt good. Once I got a promotion I tried out other classes, and slowly made them to promotion level. I think the main thing you’re missing though is that DRG isn’t really meant to be a game based around progression. Unlocking new weapons and overclocks helps, sure, but most of DRG’s progression to me is learning how to manage your resources effectively and mastering how to take down different kinds of bugs. Also, make sure you’re doing assignments! Otherwise, you’re not actually progressing beyond leveling up, and so progress will feel glacial.