If you judging system by it's ideal implementation, then you should argue for Communism (we all know how that turns out, and to what a douchy sausage fest so called "meritocracies" ends as)
Say you need brain surgery. Are you telling me you will choose based on some criteria other than results?
I will pick a 9 headed purple alien if it will do the best job. And I won't care that it had the advantage of 7 parents who were rich doctors and harvard alumni. The place to fix inequality is upstream.
The cure for those advantages is to level the playing field.
> If you judging system by it's ideal implementation, then you should argue for Communism
Straw man. Like visiting a junkyard and concluding all cars don't move. That line of reasoning lets you conclude anything with a failed example can never work.
Given those concerns, I think it is not reasonable to just say "we need to try again and try harder" because it does a disservice to those times it was tried in the past. Maybe there is a fundamental problem there that still has to be solved?
For a meritocracy, this isn't super complicated. Who decides what has merit? How will you measure this? Are the things that you measure the right things? Given that there is a possibility for side-channel information (for example, certain groups of people having terms they "look for" and that you only know about being part of this group), how will we solve this?