Your perspective is unique because of your experience in publishing. Don't let your experience get in the way of your learning. There is always something positive to say while teaching them based on your experience. By reviewing newbie writers, I find that I can jump their learning curve to a higher point of quality. And then, in return, I learn from their mistakes.
Learning how to self-edit is a key skill. You have the writing part down, far more than 99% of the writers on this site. What you need to learn is pace, construction, and how to put a book together. You know the story that you want to tell, but you aren't sure how to put it on the page. Am I right or just blowing smoke?
Either way, I found your review to be valuable because you were honest. Not because you were nice.
Just a thought