Everything has diminishing returns. GPA comes strongly to mind here. And when the MCAT gets out of hand they'll reset it like they did in 2015. Competitiveness may get so strong the gap year may become standard rather than the ~50/50 distribution it is now.
David D MD - USMLE and MCAT Tutor
Med School Tutors
How did things get out of hand on the pre-2015 MCAT?
My understanding is that there were fewer ultra high scores on the pre-2015 MCAT (39+) than on the current (520+).