There hasn't been any new content for a while. I also only get bronzes from relics. It's ridiculous how bad the relic chances are. I would give more if there were new things added. I'm not meaning new fighters, I'm meaning new missions, new variants, new elements, new anything. Master difficulty is just outright impossible unless you somehow cheese your way through it. I doubt the game will get better. You barely even get any xp unless you have a booster, and even those are super rare to get.