I'd very strongly disagree with this. If you just use grades then you are benefiting the rich to a very high degree. As the rich can pay any amount for tutors and the kids don't need to work, hence being able to use a far higher amount of their waking time for studying than someone who needs to work can.
Other factors should be factored into admissions. But the moment you agree that grades alone should be the only determination of who you allow in then you are by definition back to holistic admittance requirements.
How would you balance who to let in between a kid who has tutors and no job who gets higher marks than a kid who has to work to feed their family and has lower marks if you don't have a holistic review process?
Grades alone just doesn't seem fair and would only make wealth inequality worse as the rich get richer and the poor would fall further behind.