Sadie, it's constructive criticism just to help you improve. Self inserts are okay, just as long as you don't put yourself in it all the time. If you become an author who publishes books, nobody is going to want to read a book with a self insert in it. It's about time to ease out of the self inserts (sorry if I sound like a bitch).
I mean, sure the constructive criticism was sort of... harsh, but it's just criticism and writers need it to improve.