I'm not sure how you use Craigslist but I've primarily used the site to sell a few big ticket items - and it flat out works. After listing a couple of cars on some larger, more feature rich sites for several weeks without any traction, I listed on Craigslist, received multiple inquiries from day one, and sold within 10 days. Granted, this has more to do with the scale of the user base than the actual product, but I'm not sure you can completely separate those two aspects in this business space.
My buddy is 40 years old, not very technical, but he's one hell of a mechanic. He's been making his living off buying and selling cars off of CL since the recession started. Just an anecdote. I'm not sure an "improved UI" would help him. So many entrepreneurs are mad at CL for whatever reason, but the main one seems to be jealousy. They would rather ruin it than allow it to continue.
I found that nearly every used car I looked at on CL was either being resold by small-time "car dealers" or bought up by these same people. It was nearly impossible to find a good used car so I finally leased a new one instead.
i don't think it's just envy that makes entrepreneurs mad. CL is also quite litigious (but in a hypocritical capricious way), which is generally out of step with the rest of data-is-free, api-driven world.
It sounds like you want CL to specialize in a niche, which is something they're not really setup to do, nor is it their claim to fame. They are a firehouse of classifieds information, that's why a lot of people like them.
They could mine the data they have a bit more, but where do they stop? Should they let you select computers for sale by CPU type(newegg)? Cars by model/make/warrant/color(autotrader.com)? Dates by body measurements/race/religion/compatibility questions(okcupid.com)? Should their forums have a karma system(hacker news)? There is a reason they are called "Craig's List" & not "Craig's Apartments", "Craig's Cars", "Craig's Dating" or "Craig's Computers".
Perhaps they should try harder on the spam, but redesigning how they operate could alienate a considerable portion of their community who like the simplicity & popularity of the site.
> Most "apartment search" sites that look prettier...
None of these gripes are about appearance except inasmuch as appearance reflects functionality. craigslist is ugly, but that's not the problem. craigslist doesn't work well. I don't want it to look different. I want it to work differently.
A competing site could look much prettier than craigslist and still work no better.