for me it is often "the simpler, the better" these days. often i am sick of skilltrees, earning xp, levelling up, loot galore or long winded story heavy campaigns that turn out as a wet fart without any replayability in the end.
also, sidescrolling beat em ups are super rare these days, the best in the last years was Dragon´s Crown and that also has levels, items and stuff.
sidescrolling beat em ups were once my favourite genre back in the days, i´ve played them all and i was sad when they were practically gone.
nothing better than smashing some heads in mindlessly and destroying level interior to get powerups!
Pretty much all of this. SoR is about playing on higher difficulties and replayabiity. No filler here; just pure fun.