I have read your comments and discussion and I completely agree with you
Renderosity is a nice forum (no doubt about that )  where we can discover friends pictures and congratulate each's other work.
But critics are rarely  present in people comments.
NEVERTHELESS  it offers the occasion of meeting people, make friends and LATER ON to exchange IDEAS :  How did you do or create that effect , how did you do that ETC.....
The other way and quickest way to progress in your work is to read all the forums dedicated
to creation , or simply read books on the software you are using, texturing, how to create  plants etc...
Modeling is the most difficult part in my opinion, because it requires a lot of time or techniques
you would fastly (1 to years) learn in a 3d school .
I am a musician amateur, with 25 years of guitar ... its the same story, technique is
required at one time or another to progress in creativity and comprehension of how the music is written in order to understand  why this chord will or will not match with this one.
Some musicians are more gifted than others and can simply listen listen and listen... with a lot of practise and work and be better musicians than professional themselves but it's rare. The question is : how fast to do you want to learn ?