I see BRK as an index---an index of companies that have a good steady cash flow.

It's an index of cats and dogs.
Apple - Can buy that directly. One tech company among many, in a sector where the road is paved with the carcasses of former stalwarts.
Insurance - picking up pennies ahead of a steamroller. Highly regulated (irrational regulators in California are refusing to raise rates enough, so many insurance companies won't write new policies at all. For fire (i.e. home) or auto.) Can't make money on premia because loss ratios are above 100%. "Wonderful management in a poor business" (paraphrasing).
Utilities - Nuff said. Also highly regulated.
Rail - continuously heavy CapEx. Common carrier regulations.
Kittens and puppies - consumer cyclicals like paints and Clayton (subject to homebuilding cycle), Forest River (economic cycle), Netjets (!) No-moat businesses.

What is so great about this index? Has no significant exposure to health care or tech beyond cell phones or consumer staples. Those are proven winners among sectors for the last 20 years (at least). OK, maybe S&P 500 is overvalued. But still more promising for growth than Berkshire.

The basic assumption of value investors - that people will one day wake up and start assigning prices based on deterministic future cash flows - is flawed. It has never been true in the history of stock market. Prices have always been decided by half hype and half reason.

How has BRK stock portfolio done compared to S&P?