I think we can agree meritocracy means the best people for the job get the job. But, your contention points out what factors we evaluate when we say "best". Do we take "best" to mean when they apply for the job after years of some environment? Or "best" to mean the original genetic disposition independent of environment?

Good point. The article suggests that the original definition was more oriented to finding those with the "best" attributes at a young age and putting them at the top. E.g., 'They were the 1854 Northcote-Trevelyan report, which opened civil-service jobs to competitive examinations, and the Education Act of 1944, which decreed that children should be educated according to their “age, ability and aptitude”.'

The word "meritocracy" also implies that its a way of running government. I'm not sure if it's proposed as an alternative to democracy. I doubt that many people would think the leaders of government, the politicians, are carefully selected from the entire population base, the best of the best, so it seems that what we have now isn't meritocracy.

The point is that a true meritocracy would end up being like the situation you are talking about. In a perfectly meritocratic world, the first generation of people would succeed based on their merit, but they would use the power they gained to make sure their children have an advantage over others.

If a meritocracy wanted to remain a meritocracy, it would need to find a solution to that.