Well, considering the number of people who have started off just as bad if not worse and turned into functional and valuble members of the BVE community, I think it's worth cutting the newbies a little slack. Afterall, it's not like we're overrun with people, so the more the better.
Still, it has to be remembered that BVE add-ons are made by people in their spair time, usually around school/work, social/family lives and other hobbies, so tend to not have that much time for developing stuff for BVE, and therefore things are slow. Also, people tend to work on things that are of interest to them, and often that are easier for them to do for whatever reason (e.g routes or trains that are local to them, so they are more familiar with and can much easier get the information). This means that requests for things usually won't get a very good response, and often the best way to get things is to build them yourself. There are plenty of people here who can give help and advice and perhaps provide things like pictures or sounds (requests for that sort of thing are much more likely to be sucessful, the community on the whole is very good at helping each other).
As far as Steam goes, the main reason there isn't a lot for BVE is since BVE isn't really suited to steam, as it's based around EMUs. Even diesels arn't 100% accurate. That doesn't say it can't be done though. Also, it does seem that most BVE developers are into modern traction rarther than steam.