i've been playing on 4thewords for awhile now, and while i'm not super active in the forums, they are very, very active. it's not free, but the subscription isn't horribly expensive, and the artwork is to die for. you may even be able to see the forums without a subscription? i'm not entirely sure.
Writing
A specific community for original shortform and longform writing, stories, worldbuilding, and other stuff of that nature.
Subcommunity of Creative
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.
I use 4thewords as well! The forums could be good idea. Let me know if you want to do a co-op battle some time.
Have you tried Critique Circle? You join, you review a bit of writing from others and then you can post your own work for review. I haven't used it for a few years, but the community was great when I was using it.
Ohh that sounds exactly like what I'm looking for!
Scribophile.com also provides a very good version of this -- critique for points, then share your work, plus forums and all. Been years since I used either of them though.