The best thing you can do for a writer is leave a review. A positive review, or even a mid-level review with some insight into areas that need work.
If you come across work that is not up to par, the best thing you can do is contact them privately. Talk to them, be kind and use constructive criticism. Help someone improve and grow.
Don’t write a scathing reviewing that just says, “you suck”, or bather on about their lack of character development. This is not helpful and makes you, as the reviewer, look bad.
Even worse are reviews that really have nothing to do with the work, just — “ I didn’t like it.” How is this helpful to anyone?
My mother always said, “If you have nothing nice to say, don’t say anything at all.” Well I can’t agree 100% I think you should say something, in private to them personally.
You never know what others are dealing with on the other end of the computer. Who they are, nor what their lives entail. Reaching out can save a life, or boost moral, or maybe they’ll tell you to it’s none of your business.
Find out, leave a review — or reach out — or say nothing — and move on. Just don’t be a jerk, there are too many out there already.