First thing to keep in mind when critiquing is to look at the photo as a whole. When you're developing your eye, you need to set yourself up for success. Picture angle is important. Later on, with experience, you can guesstimate some aspects but sometimes is impossible with certain angles. Some obvious... And some not so obvious.
So when starting out, you want to look at properly set up horses in photos that are angled correctly. Here, the photographer is far too close to the front end. This distorts the image, plus you cannot critque the hindquarters at all, since they are facing completely away from you.
The other thing is the saddle. Horse must not be tacked up. Sometimes, that's the best you get, and you can do good guesstimates so long as the horse is set up well and photo is taken correctly.
So I'd not start off with a bad conformation photo if you want to learn and develop your eye correctly.