Ok, how about we get philosophical. Say there's an activity, call it A, I'm sure we agree that more than half of people can't be better than average at A. We can even think about people who train at A, there will be some ratio of the overall that the average of people who train reach (say A'). Once again, obviously the majority of people who train at A, will not be better then (A'). Now let's also say there's a cutoff point(G), and only some percentage of people can meet it, say G% (and let's say G%<A').
What does this mean. In advising people, we can say, you probably won't make G and you probably won't be better than average. Also, even if you train, you probably won't make G, and you probably won't be better than the average person who trains.
But it is incorrect to say, no one can reach G (unless G is 0%).
So if you think of this as say, swimming, this all holds, and maybe G could be, be one of the top 100 swimmers in your event. Obviously most people won't be able to do this, and unless they enjoy the process, shouldn't even (logically) aim for that G. But it doesn't mean no one should aim for 100 - after all 100 people have to reach it.
The people who do aim for G try to have training programs and schedules, and whatever else, to try to reach that G.
I'd say, this holds for almost every activity. So when it comes to investing - most people won't beat average, most people who study the market, won't beat the average person who studies the market. The real question, is what's G, what's the chance of beating the index.
If you think its zero, well there's not much to talk about.
If its greater than 0, its still true, that most people won't beat G, and will be better off sticking with indexing - so that's the best advice for most people. And yet.. if G is greater than 0, then there's interesting possibilities to try to find approaches that do work.