Poetry competitions do seem to cause quite a bit of controversy, whether because of high entry fees, the use of 'sifters' (meaning that big name judge isn't necessarily going to see your work), or because some people see the whole idea of being competitive about art wrong.
I've never had a problem with them, as long as people know exactly what they're paying for, and the money is going to support poetry longer-term, by helping with magazine or reading series running costs, for example.
Some competitions also give some sort of feedback. This could be a full critique – when I first entered the Plough Prize back in around 2003, you could pay an extra £1 per entry to get a detailed and very thoughtful analysis of your poem from the judges. It was worth entering for that alone.
But most just publish some comments from the judge or judges when they announce the winners. The usual way it's done is to say what they liked about the winning or shortlisted poems. That can have the unfortunate effect of making you think that, if your poems weren't in the same vein, they didn't like them, but it's probably the safest option.
This, on the other hand, seems pretty out of order to me. At the very least, I think the Sentinel Literary Quarterly should be making clear that if you enter their competition, the judge might well decide to be publicly harshly dismissive of your work. I think they might find themselves taking rather a hit from this, if the reaction of many poets on Facebook is anything to go by.