IMHO Craigslist is a good example of a design that nailed it right from the start and avoided the temptation to redesign year after year. Choose a region, choose the category, enter your search and bam, there are your listings. It's all bookmarkable too. What a great website.
You're not wrong but they could really afford to improve the user experience without 'ruining the design'. Unless something's changed from what I remember
- the categories page is cluttered.
- results page is messy and annoying to parse.
- the site only supports plaintext posts and has an annoying POSTing funnel.
I haven't looked but I wouldn't be surprised if there was a QoL extension made to cover all the holes left by the 'nailed design'. It's good but not great, as no web design lasts forever.