At the moment, we are headed towards 100k members… We engage many in the way you point out, but not everyone.
We are a small team still, and engagement costs time and money. We do this with a small group of alpha and beta testers. We do this non-publicly unless we are actively looking for new ideas. Playlists were an area were this was the case, as was the queue. We took that feedback heavily into consideration and iterated with the select members who were able to give us good responses and turn-around time.