Learning to mix from scattered tutorials has an ordering problem: you end up knowing how to drive a multiband compressor before you're clear on how loud the vocal should sit against the guitar. Tools get learned in the order they show up in the feed, not the order they're needed — which is why plenty of people with years of videos behind them still can't resolve a simple mix.
Mission Mode imposes that order. There are 6 worlds, one per discipline, with 20 scenarios each and 120 in total. You go through them in sequence: balance first, the foundation for everything else, and mastering last, the thing least worth touching if what came before is wrong.
The order isn't rising difficulty for its own sake: it's the order decisions get made in a real mix. Nobody EQs a track well whose level they haven't settled yet, and compressing to fix a frequency problem is the fast route to a dull mix.
Each discipline has its guide if you want the reasoning before or after playing it: EQ, compression, reverb and delay and mastering.