The problem is that many people aren't replacing their defined benefit pension with savings. They're replacing it with nothing.
That said, defined benefit pensions were always designed around the idea that you'd be staying in the same place for maybe decades. Federal government pensions are perhaps the most obvious example but it applied to many companies as well. And that just doesn't represent typical behavior--especially among professional workers--these days.
I would contend for any job that is not high paying, individuals cannot save enough to cover longer than expected age in retirement, but could cover the average.
The solution to that problem should not involve an employer. It might look something like legally mandated defined benefit pensions, aka Social Security in the US.
That said, defined benefit pensions were always designed around the idea that you'd be staying in the same place for maybe decades. Federal government pensions are perhaps the most obvious example but it applied to many companies as well. And that just doesn't represent typical behavior--especially among professional workers--these days.