Send e-mails to (especially new) users specifically about how to write a review.
I joined this community about 3 years ago, from an invitation sent directly to my e-mail, saying that one of my story in Fictionpress could be published here too.
At that time, I felt the community was so supportive and welcoming. I receive some helping reviews from various writers, stating what I had to improve, which part was unnecessary, etc.
I just got back to this community again about 3 moths ago and I felt that it was much different now. Not many replies are visible in Groups and people would hardly give you a review without you returning the favor. Moreover, the reviews I see lately are really short, just saying the story is great, there are grammar mistakes, etc., which I think doesn't help enough.
I think Inkitt should encourage new users to write more helping reviews like we, old users, used to.