Today's youngsters (under 40) will not enjoy anything like the returns their parents made

From The Economist:

... the four decades to 2021 were a golden age for investors. A broad index of global shares posted an annualised real return of 7.4%, .., global bonds posted annualised real returns of 6.3% ...

That golden age is now almost certainly over. It was brought about in the first place by globalisation, quiescent inflation and, most of all, a long decline in interest rates. Each of these trends has now kicked into reverse. As a consequence, youngsters must confront a more difficult set of investment choices

...these long-run averages are 5% and 1.7% a year for stocks and bonds respectively

Advice to the under-40 "youngsters,"

• Don't hold so much cash, ... "young investors’ preference for cash leaves them exposed to inflation and the opportunity cost of missing out on returns elsewhere." [but money market funds are yielding 5% right now]
• Hold more bonds, ... "...they have a tendency to outpace inflation that cash does not."
• Avoid “thematic investing”, ... "...Niche strategies are nothing new, and nor are their deficiencies. Investors who use them face more volatility, less liquidity and chunky fees.."