Some maps I intentionally don't play because it makes the game far too easy. There are a lot of those kinds of maps on the whitelist, and I personally don't think they should be because of that reason.
I would rather have a smaller number of maps on the whitelist and only the best which play well and are fair should get on the whitelist. There are some talented mappers out there and if they designed a map to look good, play well, and put a lot of time and thought into the design, it should be a honor to get onto the whitelist and get accepted as an officially sanctioned map.
As for mutators, the list is already rather small. I think fair gameplay is already a very serious consideration.
I do think, however, Tripwire should maintain a site dedicated to whitelisted material. Reason being is so that everyone has access to it. A forum thread (or several) is better than nothing, but finding the mutators, and the requirement of user registration to download the attachments can be a hindrance. A site would eliminate that. I think Steam Workshop offers something like this, but I can't figure out how to get the materials.
Anyway, for my servers, I stick to the official maps from Tripwire, plus a select few from the community which I think are fair for gameplay and challenging.
So my vote is FOR a whitelist, because there are some talented mappers out there that deserve recognition for their hard work.