My impression is that our planet is far off from most of their civilizations - in the boonies as we might say. Lots of times we are left alone for large spans of time and practically forgotten. Then, when they discover us again, it's like finding a source DNA that has not suffered the ravages of whatever conditions they live in on their own planet. We reproduce, breastfeed, have a vast range of emotions, create music, art, literature (imagination). Many of these qualities they have never had or have lost long ago and they now want them.

Sure they have advance technology, but they are fascinated with all we can do - with all the little knick knacks we make and create in our homes, with our attentions to asthetics in clothing, decor, nature. How we create so many ways to entertain and amuse ourselves. These things are foreign to alot of beings out there and they want to understand it. They want to feel the same joy that we feel doing the things we love. Being able to feel deeply is one reason our DNA is so valuable to them.

And, yes, as Brief has mentioned, they see the negatives as well - obesity, violence,stupidity - and they want to create a being that can experience joy without falling to the other side of the emotional spectrum into aggression. They want to keep the best qualities we have and get rid of the unhealthy, because they see are best qualities as something they would desire to have themselves.