> As a retail investor, you should buy an index fund and then forget about it.

That definitely was true.

I am unsure it is still true. Index funds have taken so much of the trade volume the are becoming momentum strategies

So long as you are happy following the market wherever it goes, and if the recent past is a guide then up is the direction, then yes.

But given the nepotism and corruption in the highest reaches of USAnian society (e.g. Trump's crypto currency scams and the blatant inside dealing and rule ignoring of the Space X float) the future looks much less certain than the past

The future always has risks but the question is that does an option better than index funds exist?