“Savings Fall Short for Most Retirees” by Tom Lauricella explains quite well that returns don’t matter when retirees don’t have enough savings. You need contributions first in order to have something returns can work with!
“You Might Be Your Retirement Plan’s Worst Enemy” also by Lauricella explains the other end of retirement planning … withdrawals. If you take too much out, then you are also going to not have enough for all of your retirement years.
Your success in retirement depends on your behavior, both before (contributions) and after (withdrawals) retirement. It is hard to retire if you do not save enough. It is also hard to sustain retirement if you spend too much (the opposite of saving).
As with all things in life, a balance is needed. This balance may be determined through plan design and prudent measurement; not by simply investing and hoping that is all that is needed do the trick.