Agreed. Even something as simple as cutting build times in half for everything until the penultimate age, in the present case atomic, would go a long way. Methinks a lot of dropoff occurs when people hit industrial, times double, and observant players realize they're still nowhere near the top. And as a result of this game tilting more and more to long-term enthusiasts they're unlikely to keep putting in the time to either be matched with sandbag accounts or late game bases they haven't a prayer against.
Through enlightenment age the game is briskly paced enough to keep rewarding you with new things, I'd wager it'd be moreso in half the time. Industrial and up is where the real game begins now. Airplanes, tanks, decoys, marginally useful factory troops. It's also where the upgrade times become a real burden too. 4 and 5 day upgrades in IA and global aren't going to make any longtimer's bases suddenly lesser somehow but they may provide those same people more targets and larger war pools by year's end.