It's still meritocratic even with dramatic genetic differences between individuals. A peer comment mentioned an anecdote of Terence nearly failing his orals because he ended spending all of his time playing Civ instead of studying anything.
It's basically the Gattaca story. Somebody can have the most brilliant mind in the world, but without actually applying it, they're not going to do great in life. If you give a person of average intellect Tao's life of dedication and work ethic, then he's going to end up a world class mathematician. He probably won't end up at the top of the top, as that's going to be reserved for those that hit the mega-lottery of genetics + dedication, but will also have no problem leaving his mark on this world and living a comfortable life.
I don't know whether Terence Tao nearly failed because he spent all his time playing Civ.
But surely you're not going to mention this as potentially factual, and then praise his dedication and work ethic... right?
I seriously doubt a person with average intellect can become a world class mathematician, let alone a decent one. Just on grid. I have seen people in college that were tremendously hard working fail math classes and just not understand it. At some point saying they should just try harder is cruel.
If it's so easy to be a world class mathematician, why can't most mathematicians do it?
"Dedication and work ethic" is almost certainly nonsense here. Some people do the activity a lot without having any ethic or dedication - they like it.