Starship to LEO is technologically conservative -- it's hard for me to believe that something like that couldn't be made to work. The uncertainty is that there's not a big market right now for launching things that size but the hope is that the low cost creates the market and maybe Starlink bootstraps it. If it succeeds as an LEO cargo hauler it can be successful without getting man rated or perfecting refueling.

Refueling to go father is technically risky and the performance often not that exciting. If you aren't able to refuel on the Moon, Starship lands and returns roughly 3.5 tons, not better than the Apollo LEM which a much larger vehicle that is tall and tippy -- landing on inner solar system bodies that it is covered with boulders.

Now it might make sense to put a full load of cargo on it, leave it on the Moon and use it as living space, storage tanks or something, but that's not the plan right now. Refueling on the Moon looks tough: water on the moon looks like a good bet, if we're lucky we find frozen carbon sources at the poles or in asteroid residues on the surface [1], but a hydrogen-oxygen rocket looks like a surer thing.

As for alternatives to local nitrogen there is: (1) producing it by nuclear processes which looks tough and (2) various other alternative breathing gases such as Argon, Helium, SF6, etc.

[1] Not clear though if we want to spend any of those on reaction mass or incorporate them in a circular economy. Actual colonists would see it differently than flatlanders. (See The Moon is a Harsh Mistress and The Martian Way)