The MCAT doesn't make or break a profession. If the student in question makes it through school, all three steps of the boards, and residency then that is a ton of education and training that person just endured and completed. They should be competent enough to treat others. All others who can't make it will be weeded out.
The MCAT is simply a standardized exam...nothing more, nothing less. Would it be great if our MCAT avgs were on par with MD/DO? Yeah of course it would but if students are making it through school and completing the necessary training their low MCAT score doesn't matter anymore.