That was the '60s, and the amount of risk accepted and stability of funding were completely different worlds. The entirety of first flight (Apollo 4) to first landing (11) was 20 months.
Today just development of the SLS has been going for as long as the 11 years of Apollo program. We have exactly one uncrewed test launch to show for it, with another not planned for 24 months later (next November) and a landing looking like 2028 at the earliest and no reason to think it won't be delayed.
