Take a gander at the PE ratio for the S&P500 over time. A substantial amount of those gains are backed by increased profitability.

https://www.multpl.com/s-p-500-pe-ratio/table/by-year

And not sure what your comment on rebalancing not being much "help" is. Rebalancing is not about "help" it's about sticking to an investing approach.

And I can recall back in the early 2000's when people said "Equity growth will never be like it was the 90's".

Glad I never listened to them.