Challenges require Game Mode X but its not available

I like the challenges but when I need to play Rush for a Weekly, I expect the game mode to be active on its own. Or Domination. Or any other really. But theyre not. Even if I filter in the server browser, the option just isnt there

Big big issue imo because it means I have to play a dozen matches and hope Im lucky enough to get into Game Mode X and then hammer out the Challenge