I agree with most things that Scorpio said, but i'd like to quibble on one point.
Surely at least part of this is that you are getting better? Beyond a certain level there's very little anyone else can do to help with your map.
Yes, of course thats true. But the point, IMO, is that certain people seem to imagine that the community here is the GOSPEL TRUTH, and that my maps are somehow inferior and should be discredited because of some "nitpicks" from community members. The point I was trying to raise is that any group that imagines this community as the absolute end all, pinnacle of TF2 mapping is deluding themselves, amazing mappers work outside of the community quite a bit more than they work within it.
As far as Valve being more vocal; it would be nice obviously, but I think we all know how busy/crazy/disorganized Valve is. They create amazing games and do so largely in secret with a twisted organic process, and I can imagine that their priorities internally are quite a bit different from ours. Spending time writing articles (because, ultimately, I don't feel like you could establish what they think about mapping in any other smaller format) on what kinds of map design's they love/hate probably detracts from other things they could be doing (playtesting upcoming games internally and providing feedback, discussing new weapon designs, etc etc).
Also, could you imagine if they did start posting directly onto certain forum posts about what maps they like/dislike? Seems like that could lead to a lot of infighting and copycat behavior. If you look at something like the SPUF, where pretty much anyone can wander in and proselytize, if a Valve employee shows up and starts talking it feels like the forum takes on a new level of insanity. I feel like Valve keeps its distance from such interactions because of the possibility of things turning to shit, of things falling apart and never really getting the right message out.
In the end, I do feel like the blog post may really be an indication of them opening up a bit more. I do also think they are steadily working on a community workshop for maps, which feels like the sort of project that really dictates what kinds of maps they are interested in acquiring. Go check out the CS:GO workshop for an example of how popular/successful such a project is, and how quickly the designers latched onto a collection of really awesome maps.