I'd say that your grades in the core courses of an undergraduate degree would be pretty strongly determined by some combination of effort, conscientiousness, interest and information retention. If you can retain the material you're taught in class and apply the required equations to it, and invest a high level of effort into all the assigned work while closely following the provided grading rubrics, you can get good grades without much writing fluency, and without much need for other intrinsic skills such as ability to come up with good original experiments or solid hypotheses to explain data.