That's too vague a definition. Like, if person A is an accomplished athlete, the best basketball player ever, I do not think his position of power or success should be, say, president. I think this is actually a very dangerous mindset derived from the capitalistic notion that success determines your--I'll call it value. If you're successful, you must be smart; If you're smart, you can be anything, even the president. Success is equal to wealth in these talking circles, and it sort of ends up as a backwards meritocracy. You gain merit measured by your success (wealth) instead of the other way around

But if you define it as a place in which positions of authority are given to people who have proven themselves knowledgeable and capable in the field in which the position of authority is being granted, I do believe in it in principle. I say that because principle and practice are rarely the same in politics and sociology. There are countless other factors that will impact your "success" that are not actually based on your expertise in the field. Better people have designed public transport, electric cars, social media, and spaceships than Elon Musk, yet the man sits in a position of tremendous influence. In a just meritocracy, we would never have heard his name

Which brings about the point that we have certain ideas as a culture (or maybe system) that awards some merits disproportionately more than others. Some will say his merit is in being a ruthless business man. He's good at that, I guess, so he should be the leader of the company. His "merit" of being a bad human being is being disproportionately rewarded compared to the merit of the scientists that actually design his spaceships, and the engineers that make them work. Meritocracy only really works in a closed system. The most capable archaeologist will be the head of the expedition. If you let the ideas go beyond that, and start comparing apples to oranges, you start seeing instead a system's idea of what's important, and by extension that of the society built in that system