If your saving rate is defined by how much you need to save for 4-10% growth to allow you to retire comfortably, you're not saving enough. Save pessimistically & then, if you're wrong, your punishment is that you can just spend more later in life.
Of course, most people aren't well-paid SV software engineers and will find themselves unable to save this much. They might be forced to contend with the possibility that saving 10% of your gross income for 40 years is not a sustainable way to guarantee 20-30 years of continual annual leave. Public pensions became popular because the masses feared what would happen when they were too old to work. Effectively, that's a welfare net for being disabled due to old age and should be treated differently from the modern retirement ideal of a healthy, mobile adult playing golf all week.