Recessions like 2008 are part of the normal ebb and flow of the markets, and we're likely heading into another one (though hopefully not quite so bad). 5-6 years earlier wouldn't have made a noticeable difference unless they were planning on retiring between 2008-2012ish, the markets have recovered after all.
Personally, if I see the stock market dip like that again I'm going to double down on my 401(k) contributions.
I already put a healthy amount into my 401(k), my employer matches $1.20 for every $1 up to 6% of my wages plus I usually get another 4% of my salary put in every April as a profit sharing bonus. I could put more in, but I’m trying to pay off debt and save for a house so that takes priority - even then I may invest in my brokerage account first to have semi-liquid assets available if something major happens and I need access to more money than I have in savings while not locking everything up in low APY hell.
If timing the dips would work consistently there wouldn't be any dips because everyone would take the risk free return until there is no risk free return left.
Of course not consistently. Just, if something becomes conventional wisdom in investing all of a sudden, there might be contrarian opportunities for a little while.
Personally, if I see the stock market dip like that again I'm going to double down on my 401(k) contributions.