I have begun to worry that broad indexes are themselves becoming a problem. As that advice seeps out, a lot of people are buying "the market". Which has long been good sensible advice, because the market as a whole genuinely produces wealth, but it's not inexhaustible.
The S&P 500 P/E ratio is up over 40, a number it has seen only twice before and both immediately before crashes. P/E is an imperfect measure, especially during a genuine crisis that results in fewer goods being produced, but the idea that "it will take 40 years to produce enough profits to return your money" is a little scary. The pandemic is certainly contributing, but it's been heading this direction since well before the pandemic.
The broad market is still probably your best bet long term, and even if now isn't a great time we all know that timing doesn't really work. Stick it in a broad index and forget about it remains the best advice. But that advice eventually undercuts itself, if everybody invests in every company regardless of its merits just because it's listed. The listing itself is becoming a skew.