What I know from talking to former Dropbox insiders is Drew really wanted to be running a consumer company. He really resisted a push to SMB and Enterprise, even though, at least to me, that seems like the obviously better business.

So not sure if it's so much that the product stalled, but that leadership actively didn't want to move in that direction for too long, then lost the advantage.

Instead they spent a bunch of energy on Carousel and Paper. (I don't have any idea how much of their eng team was working on those things)