A few disorganized thoughts:
1) A long time ago, creator names were displayed next to pools. This gave people the impression that pools were owned by individual users, which led to people creating personal pools for their favorites. Putting a person's name on something does give them a sense of ownership of that thing.
2) Most things on the site don't show the creator anywhere prominent. Notes, commentaries, tags, wikis, artists, and pools don't show their creators. Uploads are the exception. For everything else the creator isn't hidden, but it's not advertised either; you have to check edit histories to find it.
I don't think uploaders need to be secret, but I don't think they should be emphasized either. Look at Reddit or Imgur: usernames are there, but rarely do you notice or care who posted what.
3) Uploaders find validation in all sorts of things: having high scores/favcounts on their uploads, making the popular page or the Curated pool, getting comments on their uploads, having a high upload count on their profile, being the top uploader for a particular character or copyright, or being the first one to "discover" a given artist.
It's natural that people will compete over these things. Wherever there's a number or a rank, people will compete over it. The fact that posts have scores means some people will focus on uploading the highest scoring posts. The fact that profiles show upload counts means some will focus on maximizing their upload count.
These things are inevitable, whether we want them or not. I don't think competition is necessarily even a bad thing. It just needs to be channeled towards productive behaviors, not useless things like competing to see who can crosspost the top Pixiv posts every day.
4) I think new uploaders being discouraged is a bigger issue than power users being discouraged, and I think there are deeper frustrations for new users than just not being able compete for the top posts on Pixiv. The upload process for Members is frustrating in a lot of ways: no uploads for the first week, then 10 uploads per day after that (no matter how good your uploads are), then 5 months (!) of waiting to fully uncap your upload limit. The modqueue is capricious (as always) and the upload formula is inscrutable. It can take someone months of grinding to reach the 1,000-2,000+ uploads or 10,000-20,000+ edits that's become the standard for promotion these days. It's a wonder anyone makes it through without burning out.