The realism part is that we probably don’t need something that large but we could probably build something as powerful but at much lighter a weight. The defeatist part is somebody saying...”the knowledge is lost...we can never do such a thing again....bring out your dead...”bong”!
...and stuff!
the knowledge that sent us to the moon is still lost, even if we can do “better” next time. Lost it within a few decades.
I’ve been called a pessimist for saying that the future will never be like Star Trek, because the science is mostly fake. I guess sci fi nerds need their... illusions. Like many others.