The other flaw is that the time it takes to earn (save) let’s say 2M, is about 20 years at 6%. That’s saving about 4K per month.
In 20 years, that 2M has a value of about 1.5M.
Realistically, someone with a two income family can save about 50K per year. Kids cost money though.
So that would give them 1.8M. If they start at 30, retire at 50. They will never run out. They could start at 20, retire at 40. Same thing.