Problems in photos stand out to me, because I have to notice such things in my own photos. I've also been involved in photo editor and layout tasks in print media in a former age. Now I either keep the thoughts to myself or tell me wife if we're looking at something together. She's picked up a lot through such discussion and can take great photos now. It'd be rude to complain to other people about their photo unless they've asked for it or are getting paid by me.