But the other point is - as you say - you run Cradle for the loot. You're there for an obscene amount of 13★ and 14★ weapons, high-slot units and the potential for one or two good SGA adds. Since the experience gain happens on top of that, it doesn't feel as much like you're working for it as running keys does which makes it feel faster. It's a relative thing.
I'd rather get good EXP regardless of what i'm doing, instead of being limited to painfully limited missions for certain times of day or on certain days of the week. That's why i don't play much of PSO2 these days. Too dull to bother, especially due to NGS. The rewards mean less than nothing.