-- Technical challenges? No that doesn't seem right. Many of us build and scale applications far larger than this. The tools and technology are there.
-- Building a community is hard? This seems more in line with reality. Building another community like this is high risk and low reward maybe?
-- Sites like this aren't the solution any more? This could be it. But if this isn't the solution, what is?
I haven't thought of all possibilities. But really, why not just replace it?
*edit: fixed typos, typing on phones is hard.