Can you explain why you prefer red nail polish to pink? Why do you watch Law & Order instead of Desperate Housewives? Does vanilla taste better than chocolate? And if so, why?
Preference is a hard thing to put into words. You like certain things because, well, because you like them. This applies to the publishing world, too. Agents, editors and publishers like certain manuscripts better than others. Just because. Of course there are often elements one can point to---well-defined characters, evocative phrasing, tangible setting---but in the long run, these too are subjective.
Try to remember this when you go to your critiques. One person's opinion can't sink, or sail, your ship. Don't be upset if your faculty member doesn't like your work. It isn't the end of the world. Another person might love it just the way it is. Listen to the comments and criticisms, weigh them all carefully, and then decide whether to make the changes or let you work stay the way it is. But remember, it's all subjective.
You might hear something like, "It's well-written, but it's just not for me." Or, "I just don't feel strongly enough about the manuscript to represent it." Try not to press to hard to find out WHY, WHY, WHY. If there is a definable WHY, the faculty member will likely tell you. But sometimes, the WHY is just because. Kind of like when your high-school sweetie breaks-up with you and can't tell you WHY. Sometimes there's just no good answer to WHY---at least not an answer that satisfies.
When the right agent, editor or publisher comes along you will KNOW it. Just like you knew it when you discovered your spouse. You JUST KNOW. Don't try to make things fit. Don't try to MAKE the faculty member like your work if they don't. You need someone who loves your work and will support you in the lean times.
It's like that old Buck Owens song. You say tomato, I say to-mato.