I mean.. you aren't wrong, but the problem is more the diversity and resiliency of the threats. Scrapheap scrounger, heart of kiran, bomat courier, Chandra and (to a lesser extent) walking ballista are the problems. Otherwise, control would feast on these decks with sweepers. Fumigate does almost nothing against most of those cards, and you can play around settle. The RDW looks like the exception in the top 8, it's the R/B decks that really crushed. A random aggro deck always has a chance to just highroll it's way to top 8.