What’s the point of using Neeva if it’s just going to serve me Bing results with fewer ads?
A distinct focus isn't just "Bing without ads", in a similar way that Bing isn't just Google with different ads. They can have different focuses, qualities and utilities.
The UI is less important. Those 3-4 ads appearing at the top of search results can be filtered out by browser extensions.
Bing isn't just Google, because it uses a different index and a different ranking algorithm. The results are vastly different.
If a search engine is just a shell over Bing, then there isn't much point in using that over Bing.
Note DDG provides some niceties over Bing, plus the pledge that they won't share your searches with them, but you basically have to take their word for it.