I'm going to be pedantic again, but I figured there's so much wrong that has already been mentioned (like the big one, that Vulcan supression of emotion is achieved through training and constant work, not simply a genetic trait) that I might as well add something.
So, the crew get injected with something that supposedly makes them genetically "fully Vulcan," yet somehow still look like themselves, only with different ears & eyebrows...and I guess hairstyles? Since when are hairstyles genetic? And if their genes are completely altered to become Vulcan (which is ridiculous anyway), why would they maintain any characteristics of their human selves? We're all a mix of our parents and their ancestry, which is the reason for our appearances. If they're now "fully Vulcan," they shouldn't have any traits of their human parents - they should just be random, average-looking Vulcans. None of them look like they belong to the race that evolved on a hot, arid planet (of course, they already threw out the canonical look of Vulcans long ago, as well as the environment that was established of their planet).
None of it makes sense, and the writers obviously didn't care to try to have it make sense. They came up with an idea just for laughs, and it ended there. They want you to just turn off your logic (how ironic) and watch.