Buffet was richer than most nonagenarians put together in his fifties, and has been consistently generating 6x the US economy's growth over long periods. Insurance float is a neat source of capital if regulators will let you put it into equities and six decades of return usually beats four, but it's bizarre to pretend that BRK's outlying returns compared with other financial institutions come from longevity and access to capital. On the contrary, others have typically started off earlier with more, and generally donated rather less than Buffet over the last couple of decades...
The "index funds and live long" advice is sensible precisely because even the average savvy investor isn't likely to time value investments as well as Warren Buffet did.
Index doesn't go up. Individual stocks do. I mean a small section of the stocks within the index contribute to most returns. This is of course different in a bull market where lots of them go up at once. But even in choppy and bear markets, its a small section of stocks that do most of the upward movement.
You need to study index carefully, like pick each stock and study it. You will see Buffet isn't exactly investing outside the index, his investments come from inside the index.
You are not looking for needle in a haystack here. More like a thick loaf from a pound of bread. If you squint enough, you find them.
The "index funds and live long" advice is sensible precisely because even the average savvy investor isn't likely to time value investments as well as Warren Buffet did.