Vanguard, for example expects a 2.4%-4.3% annualized return on equities over the next decade (3.35% is the midpoint), and Schwab also has about the same forecast
Here's what Google served up on Vanguard, an October issue, there might be something later... but anyway
https://advisors.vanguard.com/insights/article/marketperspectivesoctober2021
because of very high valuations due to the factors you mention, and so interest rates suck on the alternative investment: bonds, CDs, etc. (in large part because of Federal Reserve QE action).
And no, we don't know the future, we could be at the beginning of a period for U.S. equities that make the Nikkei's experience look like a walk in the park.
And yes, the mid-60's to early 80's period was a long and difficult time for stocks. As were the 20's and 30's.
I remember "The Death Of Equities" Business Week Aug. 13, 1979 cover page all too well.
https://www.google.com/search?q=%22The+Death+Of+Equities%22+Business+Week&newwindow=1&sxsrf=AOaemvLcmFSTqtvwPL1Iqmo9CxsHyXtFWQ:1638495265819&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjLz6PCvsb0AhXJVc0KHcqJAYUQ_AUoAnoECAEQBA&biw=1063&bih=605&dpr=1.1
For a longer term perspective, I Imgur'd this graph from Yahoo Finance at near the bottom of the Covid crash. I try hard to keep the longer term perspective in mind. Those were some mighty frightful crashes. The thing is, after several doublings, a 50% "crash" just gets rid of one of those doublings.
https://www.democraticunderground.com/10142452432#post14