It's true: The majority of the maps is lacking of purpose.
Why?: If you build a map you often have an initial idea about something you want to see ingame. This can be something regarding the gameplay, like a unique trickjump or a well-designed layout. It can be some sort of setting, like a realistic town, the surface of an asteroid or a underwater cave. Or the map can evolve around a story or "purpose" which in most cases also defines the setting.
Fact is that Nexuiz is a fast-paced FPS game without any story-driven elements, so the focus is definitely on the gameplay-side.
Players who are into the game are focused on playing it and not on understanding the environment. But if a new player plays a map for the first time it's good to give him the feeling of entering an environment that makes sense in some way. He'll then be more motivated to explore his environment and such gets more involved into the game-world. So to attract new players, this is the way to go, but it's optional .
The problem i see is that many maps lack of atmosphere, a defined continous unique style and details. You don't need to explain why there's a moving brush in your map, but you need to have it all fitting together somehow. Having a purpose for such elements helps in this task but is not mandatory to make a good map for Nexuiz.
And yes: Making it all fit together and polishing the details takes a lot of time, which many mappers don't want to invest after they finished the basics of their initial idea.
Art needs time, and without artists (mappers are artists) taking their time, the maps they produce won't be polished, won't involve the player into the game-world and always will have that "unfinished" feeling about them. Still they can be fun, but they could be so much more...
A lot of maps out there are filled with good ideas, some are working with Nexuiz, some are not, but in most cases they are broken by poor realisation on the technical and the stylistic side.
So my advice for all mappers who want to produce good maps: Take your time! Test your map! If you don't feel satisfied with the result, change your map! Look into other maps that work for you and try to figure out WHY they work! (what architectural elements are used to produce a certain feeling? How is it lit? What size is used? Why is it fun to play on it (what are the major gameplay elements)? etc...)
Also take criticism to learn how to make better maps.
That's where i would like to address the players who give feedback: Be honest. Don't be an asshole, but give constructive feedback. I can't read posts like "Whoohoo. Ur m4p r0XX" anymore when it's obvious that a lot of crucial elements for a good map are missing (most of the time it's the texturing, the lighting or the item placement). It's those details which make for good polished maps, and mappers need feedback on those! For example there are often misaligned textures somewhere which just are overseen by the mapper. Point them out! You're not nitpicking, you're helping to improve the game experience!
And we need more modelers to make map-objects
btw.: Comparing Nexuiz to kkrieger regarding the visuals doesn't work, as kkrieger is a singleplayer game, thus gives the designers much more possibilities to guide the gamer's attention and involvement via lighting and scripted events. Nevertheless Nexuiz needs more eye-candy in these days.
Heh... /me posting
bleach->aneurysm->straledm5->dieselpower->space-fun->o-fun->runningman->runningman1on1->aggressor(conversion)->soylent->bloodprison->bluesky->ruiner->reslimed->strength