Notably, Warren Buffett essentially exited the stock market over the last few years because he believes all his investments were massively overvalued.
That does paint a pretty grim picture wrt potential stock growth, if this finally triggers the correction back to a more sane stock price (last I read about it, you'd have to hold the stock for 65 years for the investment to break even).
The current stock valuations are essentially based purely on the same mechanic that makes Ponzi schemes to successful... At least short term.