If the community you want to attract can do things more the way they want with your technology, you've solved an important part of the problem. For example, reddit's "Recommended" section is an attempt at that.
I-and I suspect everyone else reading YC News-can probably think of dozens of tools that I'd love to see (and if you're a reader you've probably thought about this too and are thinking of starting a company to build this tool).
When I said: "Today, all the good tools already been taken."
I meant for obvious to be included as part of good. Of course there are literally more tools to be made, but there are probably easier ways to create value than finding the one perfect tool that no one's thought of yet.