> Your problem is you can't define meritocratic in a way that everyone will agree with
Of course you can't. One man's merit is another man's vice. The very notion of a meritocracy is literally a sarcastic joke [1].
But the problem is even worse than that. EVEN IF if you could define a universally agreeable "meritocratic" system, you would still have the problem that people with power would abuse the system to lock out others.
Suppose 100% "meritocratic" people were selected at random. They then immediately change the rules. Now 99.99% of people disagree with the legal definition of "meritocratic". But tough shit, cause this ain't a democracy, and the other 00.01% of people have all the power.