Funny you should say that, because I think it *was* something of a slow cycle. I mean just compare the level of technology the Protheans achieved before the Reapers arrived and what the council races had at the same stage. Not just technology, but exploration too as the Protheans were much more widespread. They also had a single united government, whereas Citadel space isn't governed centrally, but co-operatively through the council and even then about half the inhabited galaxy it made up of independent or rogue states like the Batarians or the terminus systems.
Don't know if this is the intent, but my theory is that the Asari (unintentionally?) held back this cycle. Their long life span makes them a lot slower to institute change or adapt to new circumstances and their preference to mate with other races may have engendered an almost instinctual compulsion to act through proxies. This is pretty evident in how they reacted to the Rachni wars, the Krogan rebellions, the Geth/Quarian conflict, the arrival of the humans and their headbutting with the Batarians over colony rights.
In each case, rather than meet events head-on they try to distance themselves from any conflict and where that's inevitable, they tend to get other races to do a lot of the dirty work. A reliance on diplomacy over aggression sounds nice, but the Asari take their passivity almost to the point of total indolence. It's almost as if their ancestors' first instinct was to sit perfectly still and wait and see if they can just outlive the big scary predator that just crept in the cave-mouth.