I'd worry about your definition of "best society". Is the current system an existence proof in your mind?
Yes, the current system (Western-style democracy, capitalism, freedom, markets) is the most meritocratic of all systems realised so far (AFAIK), but that doesn't mean we can't do better still.
Human instincts and morals are really well calibrated to small-village life. I take things like the Dunbar number [1] to indicate that we are optimised for a small circle of close relationships.
"Fairness" has a sister in "equality" that is very powerful force on the local scale and scales horribly, to the point where equality being scaled up is usually a warning sign of an incoming economic breakdown where everyone starves. Unfortunately, people keep trying to scale equality up because they want it in their local relationships.
Talking about "permanent power disparities" touches on the same vein of thinking - we know that permanent power disparities are an inevitable feature of society. The attempts to set up societies where there are no permanent power disparities have resulted in permanent power disparities forming, and frequently going to very nasty despots. Modern western civilisation has done _extremely_ well compared to the competition by dangling systemic advantage as the reward for massively improving the industrial base and consumer access to resources. This has worked a lot better than attempts to suppress inequality under, eg, the communist systems.
Whether luck is involved or not is of little interest to me. I think we obsess too much about money and tie it too much with human worth. In part because we like to think of ourselves as meritocratic, some of us feel compelled to justify our wealth differences to ward off the envious (plenty of that to go around). I'm not sure how you tie this into creating a "best society". I think arguments can be made that intersections of money and power/power and ambition are the most dangerous. Indeed, an argument against democratic republics is that those with a lust for power will tend to seek office and once they have it, believe they are entitled to it because they merit it as a result of their own actions. Hereditary monarchs, on the other hand, know fully well that they didn't ascend to the throne through their own efforts and that they are in a position of responsibility w.r.t. their people. (Note that most monarchies were not despotic despite the folklore because they were checked to varying degrees by tradition, the lords, the Church, etc, and were guided by advisers who brought their knowledge to the table, thus divorcing expertise from that bounded and constrained power.)
This is a frequent criticism that is IMO completely off base. Nobody is saying that this world is particularly meritocratic (although I think Western-style democracy+capitalism+markets is experimentally the most meritocratic system ever realised).
https://en.wikipedia.org/wiki/Donald_Trump#Family_and_person...
To all "proponents" of "the luck argument": there are thousands of people far more lucky than Elon and Steve (born to wealthier families, smarter, better connected, etc) that didn't achieve what they have. So... luck obviously isn't the answer.
Having said that, even if luck were the answer, I'd still support meritocracy, because it results in the best outcome. It's not about fairness, fundamentally - it's about creating the best society. If the only people who can do that are "the wealthy" (or whichever category you choose - most likely "the intelligent" these days), then so be it - it's best for all the rest of us if they "rule", meritocratically.