Looking at Wikipedia, maybe its just about money.
"Apollo ran from 1961 to 1972, with the first crewed flight in 1968" - $25.4 billion (1973)
"The Space Launch System (SLS) is a US super heavy-lift expendable launch vehicle, which has been under development since its announcement in 2011. It is the primary launch vehicle of NASA's deep space exploration plans,[12][13] including the planned crewed lunar flights of the Artemis program and a possible follow-on human mission to Mars.[14][15][16] SLS replaces the Constellation program's Ares V launch vehicle of 2005, which never left the development phase." - For fiscal years 2011 through 2018, the SLS program had expended funding totaling $13.999 billion in nominal dollars.
In 7 years Apollo had crewed flight. In 7 years SLS isn't even off the ground, and that is after the previous project never finished.
So, how do we gain public support for funding these missions? Honestly, while 'war' may be an answer its not a good one.