You are right that top universities already use non-grade factors, but this supports our side! It proves grades alone cannot capture real merit.
Yes, merit becomes less numerically crisp, but fuzzier does not equal less fair. A simple number may look clear, yet it narrows merit down only to exam skills. That kind of sharp clarity comes at the cost of ignoring creativity, character and practical virtue.
Merit itself is naturally diverse; it was never meant to fit into one single score. The problem of current meritocracy is forcing complex human ability into a narrow GPA metric. We accept some mild ambiguity in exchange for a fuller, less distorted picture of students.