Everyone is a critic. At some point, some person will comment on your writing in a very blunt, no-nonsense terms. Others will only offer cheery comments with no real meat. Some will like your voice, others will not.
Everyone has an opinion and some aren't shy about sharing. And with the internet, they can do it behind anonymity. I'm sure it's disheartening for authors when they discover someone they thought a friend or professional associate is the one dissing them and/or their book. And that does happen.
Some authors win the big prize, others won't--NY Time & USA Today bestseller lists, contracts that keep on coming their way. Sometimes luck plays a bigger role than talent. That doesn't mean you're not talented. People just didn't "vote" for you by buying your book. I'm not suggesting that poor books make the lists. It might once, but for continued success, an author has to write a compelling book every time.
Or maybe your book just came out at a bad time. There are other things people are spending their money on like Christmas presents.
When it comes down to it, most things are out of an author's control. God bless you if you're a control freak. Publishing is NOT the business for you.
All we can control is our process and how we tell the story. No book will get written if you don't insert butt into the chair. No book will get published if you don't send it out into the world and face rejection.
So if someone makes a Simon comment just smile and thank them for reading your book. Now, that may really drive them batty.
And, hey, if a 27-year-old, gray-haired man can be America's Idol, maybe there's hope for me to sell once again.