Actually Megumi is a rather great cook, probably better than some of the others. She's just still a unsure of her abilities, plus in my opinion Rindou didn't seem interested in failing them mainly because that's just not her style, also she finds the rebels entertaining and I think she has a soft spot for Megumi
I agree. Megumi has very low self-esteem that's why her potential doesn't always come out to the fullest. She could even be better than Kurokiba and the others once she acknowledges how skilled she is. The thing is she has both the skills and luck, which others lack.
Soma was never discouraged, but megumi sure is lucky. It is so unfair Nakari got expelled and all the other better cook.