It is not my experience that reviewers are overly critical. The notes I have seen fall into three categories: 1) pointing out the nagging issue that I knew but

It is not my experience that reviewers are overly critical. The notes I have seen fall into three categories: 1) pointing out the nagging issue that I knew but avoided, 2) misunderstandings, which are annoying but show how the paper is not clear enough, 3) genuine insights which I would not have seen. I have never wanted these to be more positive, but I can see the benefits such a cultural shift would have. Phrasing the notes as positive feedback would benefit the happiness of the authors, but make the notes lengthier and increase the effort for the (volunteer) reviewers. I wonder if the editor could reframe the reviewers' notes to improve the tone before sending them to the authors? At least in chemistry where I work, a rejection rate of 9/10 at the review stage would be very unusual. It is possible that reviewers in the triage stage are harsher but I never see these reviews.