"If you look back to the history of the Apollo program, in-orbit rendezvous, vehicle assembly in space, and refuelling were all discussed, then discarded as too complex and risky. Instead, the Rocket was built big enough to do the whole job."

And you didn't specifically mention, too costly [though "complex" suggests this].
And they were right.
But you must realize what they were attempting to do. If for example, the Russians got to the moon before the Americans, one could say much of the American space program was a waste of time and money.
And getting to the Moon in the shortest period of time, can also be the cheapest way to get to the Moon.
There is no question that the Saturn V route provided the quickest way to get man on the Moon and safely return them.

But Saturn V was too expensive to maintain and having govt building and operating rockets is generally a bad idea.

But the *ultimate/total* cost of Saturn V in terms of what it "did" to America's effort to "open the space frontier" was extremely costly.

American was opening the Space frontier [before Sputnik], in a gradual and rational approach [E.g. X-15 program]. Now, 40-50 years later we are going back to that "approach" [sub-orbital space tourism {SpaceShipOne, etc]. This sub-orbital approach will probably a major factor that results in opening the space frontier.

But if there was a choice between sub-orbital and gas stations- I would choose the gas station step before the sub-orbital step as the faster and surer route to opening the space frontier. Needless to say I'm glad we appear to be doing them both.

"How is a gas station in space better than ISS?"

Well, a gas station could like ISS- and that would be mostly a waste of time. Or one could say that a reason the ISS is lacking is precisely because they dropped the idea of ISS being in part a gas station and spacecraft servicing station. Personally, I think that if ISS was a gas station, then the same forces which make ISS mostly a waste of +100 billion dollars would be in play- though it's vaguely possible that commercial forces could move that which is unmovable.

One could say that in a sense, ISS is a gas station- which is exclusively supplied by Russian spacecraft, but this fuel resupply is only to keep ISS in orbit rather than get any spacecraft beyond orbit.

"(Well, I admit it does then enable Lunar and Martian missions with our current crop of underpowered "heavy" lifters) But it also requires managing and station-keeping and regular rendezvous missions to gas it up.

It's basically ISS with an attached bowser. "

Our current crop of "underpowered "heavy" lifters" are barely commercially viable [without US military contracts, they wouldn't be]. An even larger lifter would be not economically sound. And merely because something is not economically sound, it does not mean that govts [tax payers] should pay for it.

Whether any gas station will "work" depends upon if there is a monopoly supplying it- and having a govt function as that monopoly would worse than if was a private monopoly.

Or in other words, if it's not market based, it won't work.