Sorry that I can't answer your question in detail. I was listening to a podcast (maybe NPR or maybe some other interviews), the reason Apollo style program isn't used anymore is because it's not sustainable. I didn't understand the technical detail to give you a good answer.

Apollo was feasible because there was a very real risk of the entire USA being destroyed and every voter knew it. It was a race to technological and military superiority against the USSR and the Apollo program was a big part of that. That existential fear and risk doesn't exist today, there is no appetite for that level of commitment in the general population. AOC herself could kill a program proposal like Apollo with a single tweet about proposed bathroom door labels.