I used to think along your lines.
When I would draw something, and post it for others to see, something I spent hours on, the general response was usually negative, and I thought people were ignoring the positive aspects. The primary reason people typically focus on the negative aspects is, if your intent is to improve, you need to know what's wrong, not what's right. If something's so right that it avoids the pitfalls of the wrongs, then people will notice, but until you pull yourself up to a level where that's possible, you'll be hearing a lot of what appears negative, but it's exactly what you asked for: criticism, or insight as to what people think you are doing wrong. This is oft objective to the degree that their experience might trump your own, and sometimes subjective nonsense (reportable flames). Bear with it, and you'll improve, ignore what they're saying and stagnate. The choice is ultimately yours to make.