What is "something safe"? I was under the impression that 401ks are not really known as risky investments.
Within their 401k, most people hold a higher percentage of stocks (more to gain) earlier in their working life and transition to a higher percentage of bonds (more stability / safety) later in life as they approach retirement.
Good concrete examples of what to hold are Vanguard's funds which are low cost and own the whole stock market because they're index-based. VTSAX for stocks and VBTLX for bonds.
https://investor.vanguard.com/mutual-funds/profile/overview/...
https://investor.vanguard.com/mutual-funds/profile/overview/...
There are also target-date funds (also called target retirement date funds) which automate the transition from stock heavy to bond heavy based on a future retirement date, and you pay extra for this benefit, but BE CAREFUL as many of them charge significantly more fees than doing it yourself.
Vanguard is one of the best (lowest fee), so for example, their TDFs have a 0.13–0.15% expense ratio while the two index funds above have ERs of 0.04% and 0.05% respectively.
It is not uncommon for the more popular mutual fund providers to have radically higher expense ratios in the neighborhood of 1–2%+ (in addition to other more subtle fees). The difference might sound small but compounded over decades, the effect is massive. (There's a reason people working in finance are paid so well.)
Even working in quant finance and managing these portfolios for huge pension or retirement plans, you get astounded that the “technical experts” on the board of directors barely understand the concept of simple interest, and continuous compounding or any formulas would be untenably way, way too complicated.
So when you see people on Hacker News acting aghast that elderly people might have inadvertently been loaded up on high-beta equities right around the 2008 crash, you just know those commenters have no concept of the reality that most Americans live through.
In my grandparents case they even went to some local Edward Jones financial planner or something who just turned out to be deeply incompetent and acted like he was some hot shot day trader, putting them in equity-heavy niche portfolios with higher fees, when they should have been decorrelating themselves from market volatility generally.
He did nothing illegal, and my grandparents believed earnestly that someone competent was making prudent decisions about their money.
But this description was very technical, another way to approach it is: keep in mind that there is no 100% safe way to save money, if you are looking to set money aside for retirement you may just put it a "retirement fund" based on the year you plan to retire (or a bit earlier to be conservative).
For example the "Vanguard Target Retirement 2010 Fund" lost 21% in 2008: https://investor.vanguard.com/mutual-funds/profile/performan... (but gained 19% in 2009 and 11% in 2010).
Edit: I agree that access to the information is a big problem for the common people. This is a valid general concern outside of just planning retirement though.
https://www.amazon.com/Simple-Path-Wealth-financial-independ...
One beef I have with the finance industry is that very few people, especially professionals, will give you the above info in an actionable manner to do it yourself. And given the way they are compensated, it's not a big surprise. I would like to see it more open and approachable like programming. But I do believe that the average person can understand the basic concepts of buckets, index funds, risk allocation, and reducing risk over time.
I do think that the weird high-fee niche investment case is unfortunately quite common. Perhaps one more big idea for most people to understand is that even most financial professionals can't beat the market, though it almost goes against their own compensation incentives to admit that.