I thought that the Reapers drove our technological advancement in a certain direction and any adjustments we make to their tech is relatively minor. I always considered the galaxy in ME to be in a state of technological stagnation, which is how humanity caught up with the other races in a relatively small time-frame. The Asari should be almost 3,000 years ahead of humans technologically, but instead they appear to be barely more advanced at all.
^That's more or less how I see it. The Reapers are billions of years old and have reached the pinnacle of what technology can do; they don't need or want more toys, especially not cheep knock-offs of their own stuff.
As to what they ARE after exactly , it's still a little unclear but as I said above, it seams to have something to do with whatever make a race unique. I suppose you could call them soul stealers and you'd probably have the basic shape of it, though that's probably still not quite the right terminology....but close enough.
As for the Asari, while I'd certainly agree they're resting on their laurels a bit, it should be noted that because they're so long lived, they've "only" been on the Citadel for what amounts to a couple of Asari lifetimes. That really isn't a very long time from a cultural standpoint. Human civilisations have certainly gone more or less unchaged for (relatively) longer without completely stagnating.
Mind you, apply that logic to the Salarians and it's a wonder they make any progress at all!