Riot: We've noticed players don't like being forced into certain map or mode in missions
Assumed meaning: So we will try to balance mission so that they can be fairly accomplished and enjoyed by players regardless of whether they play SR, TT, ARAM or RGM.
Real meaning: So we'll make 1/3 of missions bound to SR objectives or much easier to grind in SR and 1/3 literally requiring you to play SR and 1/3 impossible to achieve. Yolo.