I'm not saying the old system is perfect for today's workforce, but 401k (or similar programs) are really not the right solution.
There is an inherent problem with defined contribution retirement plan - you just can't know how much money you're going to need in retirement.
And I'm not talking about the case of people who are unable or unwilling to do that calculation (although in practice it's a big problem as evident by the sad amount the average American family have saved for retirement) even if you're super knowledgable about that stuff and do all the research that needs to be done, without a crystal ball, it's literally impossible to know how much money you're going to spend between your retirement and your death, it's a curve of probabilities.
So the prudent thing is to oversave, i.e. make sure that it's 90%-95%-99%-whatever chance that you'll die before you spend all your money, and that's not a good thing. On the personal level on average people will save more than they'll need, so they'll have less money to spend while they're alive (sure, you might get "lucky" and have a ton of expenses in your retirement, but on average if everyone saved enough money so it's very unlikely they'll run out of money, they'll be saving more than they need) and on the macro level, this is a wealth transfer from (mostly) working people to the financial sector (something I personally think is not good for the economy or society).
It's like running an insurance for one person, you're not spreading the risk. Now consider a system where everyone put money into a single pool (which in general how defined benefits plans works) in that case everyone only have to save the average* amount needed for retirement and as a whole, people on will have more disposable income that way.
* yeah, it's probably not exactly average, this depends on how you want to distribute the benefit and to what level you want to tie them to lifetime earning, I'm simplifying things a bit here, but as a whole it's undeniable that you'll have to save much less under such programs.