I agree that it is interesting and possibly important to think about whose views count as "elite."

The key question here is, "If a broad coalition of highly trustworthy people were aware of the considerations that I think favor investing in index funds, would they switch to investing in index funds rather than investing in actively managed mutual funds?" I think the answer to this question is Yes. By and large, my sense is that the most trustworthy people who are investing in other ways aren't aware of the considerations in favor of investing in index fund and the strong support for doing so from economists, and would change their minds if they were. One reason I believe this is that I have had conversations with some people like this, convinced them of the evidence I have, and this convinced them to switch to index funds. They did actually switch.

In case you missed it, I discuss who counts as "elite" here:

How should we assign weight to different groups of people? Other things being equal, a larger number of people is better, more trustworthy people are better, people who are trustworthy by clearer indicators that more people would accept are better, and a set of criteria which allows you to have some grip on what the people in question think is better, but you have to make trade-offs. If I only included, say, the 20 smartest people I had ever met as judged by me personally, that would probably be too small a number of people, the people would probably have biases and blind spots very similar to mine, and I would miss out on some of the most trustworthy people, but it would be a pretty trustworthy collection of people and I’d have some reasonable sense of what they would say about various issues. If I went with, say, the 10 most-cited people in 10 of the most intellectually credible academic disciplines, 100 of the most generally respected people in business, and the 100 heads of different states, I would have a pretty large number of people and a broad set of people who were very trustworthy by clear standards that many people would accept, but I would have a hard time knowing what they would think about various issues because I haven’t interacted with them enough. How these factors can be traded-off against each other in a way that is practically most helpful probably varies substantially from person to person.

I can’t give any very precise answer to the question about whose opinions should be given significant weight, even in my own case. Luckily, I think the output of this framework is usually not very sensitive to how we answer this question, partly because most people would typically defer to other, more trustworthy people. If you want a rough guideline that I think many people who read this post could apply, I would recommend focusing on, say, the opinions of the top 10% of people who got Ivy-League-equivalent educations (note that I didn’t get such an education, at least as an undergrad, though I think you should give weight to my opinion; I’m just giving a rough guideline that I think works reasonably well in practice). You might give some additional weight to more accomplished people in cases where you have a grip on how they think.