Why bother?
You mistake honesty for cruelty. It's a common problem here, but since I take my writing seriously and that of others on this site, I strive to never mistake one for the other.
I've been told my reviews can be harsh. I acknowledge as much in the introduction to my review forum. It's been suggested that I should avoid crushing the frail petals of someone's creative impulses underneath the jackboots of objective analysis, but I have to ask, why else would I be here, in a community of writers rather than holing up in a dark room in front of a screen? There are friends, lovers, scout masters and mothers to be concerned with emotions, if that's your priority. It's called
Writing.com, not
feel_good.com. I'm concerned with the writing, and if someone is off track, pretending otherwise is the real act of cruelty. Ignoring them altogether to avoid being honest is simply self-indulgent.
I make it a point to only write a review when it's specifically requested. In fact, I go out of my way to scare off any prospective customers who might only want their viewpoint to be validated and fed back to them. After that, if they still want to know what I think, shucks: I feel obligated to tell them.
Here's the thing that no one mentions about reviewing: it's the opposite of free advice, or empty kudos. A review requires one to get down in the mud with the writer, to participate in the same process, to examine themselves as well as the writing and to be honest about themselves, what they know, what they don't know and the struggle to learn. A good review teaches the reviewer as well as the writer, and it is that willingness to speak from ones own struggles with the craft that will offer something useful to others.