Hardcore MMA fans are, by their very nature, ignorant people so I can see how they would have trouble appreciating Rousey, but I do appreciate her.
Rousey did more than any other fighter to bring MMA to mainstream status. She has a bad attitude and her skills were insanely overhyped, but that is irrelevant since she was great for the sport.
Rousey tapped into a cultural movement in a way that nobody could have planned or anticipated. She tapped into the Feminist agenda that the mainstream media has been pushing hard for the last few years. Since Rousey was a woman and she was successful in a man's sport, she became the darling of mainstream media and the UFC got tons of free positive press coverage.
Casual fans fell in love with her, not because of who she was, but because of what she represented. We should be grateful since MMA becoming mainstream means many good things, including: better athletes coming into the sport, higher pay for the fighters, more events, a bigger fan community, etc.