sorry, but "always be in the market" is a rule predicated on a period of history that's been especially kind to the good ole' usofa. there is absolutely no guarantee or even reason to believe in a guarantee of the same going forward.
here's something to think about, and i know i'll take downvotes to hell for all this: if everyone agrees and everyone is investing (for retirement etc) identically (long stocks bonds whatevers), what are the odds it's "cheap" or represents future extraordinary gains?
"Always be invested in the market" - what does it mean? Always have at least something long in your portfolio? Always be 100% long in your portfolio?
If I have 99% cash and 1% in VTI for 10 years, am I "always invested in the market" during this time?
I'm glad you don't adhere to the defeatist approach of Efficient Market Hypothesis proponents. Always be in the market, yes. Always follow the market, no.