Really, I think this comes down to the fact that WowAce, not Ace, should be the one being advertised, if anything, to both users and developers. A WowAce mod has easy updating (and uploading), quick bug fixes and translations (thanks to the svn), and a strong, dedicated community.
Again, not an Ace thing. SharedMediaLib shoudln't even use Ace.. its stupid that it does. Any addon already can (and I'm sure do) hook into the library if users intend to use it.
No, the problem is that it's only an Ace thing. Many Ace addons/authors use SharedMedia because most people in the Ace community know about it and it's a great library. The problem is that I don't think authors outside this site know that they have this powerful library available to them. Also, I think some nonAce authors are discouraged when they hear Ace being thrown around because Ace is a community and they are just one person. I believe we need to open the lines of communication and have this community spread out into other places to spread the wealth of knowledge (like the fact SharedMedia Exists) and creativity of this community.