For all of its problems, the core concept of a meritocracy is that you don't get positions in life simply based on ancestry.

If the children of an astronomer really do turn out to be the best astronomers, then a meritocracy should theoretically allow them to become the best astronomers in the next generation.

But they do not get to be the astronomers JUST because they had a parent who was good at that. Every generation gets a reset; if genetics really do predict merit, then sure, the arrangement will look a bit like ancestry.