Yepper!
But you can't hoist the necessary mass to the moon on it. That's the point I think ptyor is missing. It wasn't Nasa - it's just physics.
L/K upper stages would require massive amounts more fuel weight. Which would require an even larger boost dtage.
That, BTW, was the Russian design approach.
Apollo was technological magic - writ larger than life.
But, sadly, we threw that technology away.
Or let it slip from our fingers - which is kinda the same thing.
So far, I have to admit, I'm rather disappointed with the 21st Century.
Gimme the good old 20th any day!
Richard