Dance isn't just about being technically perfect and following the rules. Its about how it makes you feel.
I think volver has a point here. I might have said before, (NOT boasting), that I went to dancing lessons 3 times a week, and have a haul of over 100 medals, some All England Dance (Sunshine competition) finals. I certainly wasn't the best dancer or the most technically perfect, but I danced with feeling and expression. All the other mothers just knew I would win the character classes, the song & dance and the national class, but when it came to boring tap I found it difficult to put an interpretation on the dance and so never got highly placed.
Just like in Strictly, different dances suit different people. Molly, having gone to theatre school, would have had instruction in the various styles and her training showed, but maybe she was too polished for what the show wanted. I think the same thing happened to Ashley Roberts from PussyCat Dolls who had studied modern dance and was by far the best dancer. Stacey Dooley won, even though she wasn't a dancer, but the public liked her more.