We shouldn't try to do it the same way we did in the 1960s. We have a different industrial base, and in spite of the jackasses in Congress, we've learned a lot about rocketry since then.
Back in 2013 or so, NASA had a team look into what it would take to build an F1 class engine using then current technology. The team studied the specs for the original F1, read the design documents, examined the blueprints, studied actual examples, and then set to work. They designed an engine they called F1-B, which would have been simpler to build, lighter, and higher in thrust than the original.
Congress killed it.
Instead, Congress mandated that NASA reuse Shuttle parts, rather than building something new. It would be cheaper, you see ... except that it isn't and no sane person would expect it to be. The result is this technological abortion called "SLS".
People are quick to blame NASA ... NASA only does what Congress mandates it to do. Blame Congress ... and the people who put congressthings in Congress.
The nugget of the problem right there. Additionally there are military projects that were done under "black" budgets that cannot be made public for various reasons that would make this much simpler if that technology could be used. One part of the government isn't even allowed to talk to the other part.
Civilian programs and agencies would be gobsmacked if they knew what their military (and classified contractors) have been up to for the past 40 years or so.