You should be mad at the Capitalists not the workers.
This is one of many ways that folks aged 70+ had it much better than folks in the workforce now, and represents generational inequality that you should not minimize or attribute to "capitalists."
You may, if you like, attribute it to "generosity" by individuals indifferent to "math."
Shouldn't a reasonable business have been investing forward to avoid this problem? IE, you don't use todays dollars, you use yesterdays dollars.
Its seems the flaw is that they lacked sufficient savvy to invest the pensions in a way where it would be able to build upon itself.