How trite.
No one has ever ever ever ever suggested MCAT scores predict what kind of doctor you're going to be. They DO, however, measure what kind of a student you are, how good of a test-taker you are, and how good your basic science background was, in a standardized way. And I've got news for you - succeeding in medical school requires a strong student, a good test-taker, with at least a bit of a knack for science. I guarantee a med student's grade in embryo (or USMLE sub-score) has absolutely no correlation with what kind of clinician they become, but they're still required to take it and, yes, pass it by demonstrating they understand it at a minimum level. Should we cut it out of the curriculum since the impact on "clinical competency" is practically non-existent? No.
You hear premeds explain away deficiencies with BS excuses like, "oh, I know the material, I'm just a bad test-taker" as if it's some sort of reprieve. I think "I have test anxiety" is the most ridiculous one, personally, they say it like it's a disease or something. What are you going to do when you're on the wards and an attending pimps you? Hand them a note from your shrink informing them you aren't responsible for spouting off the sequelae associated with lupus because it makes you anxious? Sorry, but unless you're so blatantly smart and capable that you get into Yale (which doesn't have required exams), you're going to have to be good at taking tests to pass your courses, and even then, you still have to pass the USMLE, which is the biggest exam of your life. And you will have to be a good test taker (i.e. do well on the USMLE) to even get INTO more competitive fields.
So while OF COURSE the MCAT doesn't predict "what kind of doctor you're going to be" (good/bad), it's ridiculous to say therefore it means nothing. Keep in mind there are plenty of applicants who have everything the lower-scoring (but good in every other way) students have....personality, character, leadership, work ethic, etc.....but DID do well or reasonably well on the MCAT. It's not like clinical competency and MCAT score are inversely related. And you're nuts if you think a solid basic science foundation doesn't help your clinical competency.