The path taken in the 1950s for spaceflight was dictated by its funding source -- missile development. Missiles were optimized for high performance and were single use devices.

Even when dedicated non-military rockets began to appear, e.g. the Ariane range and the Space Shuttle, they had dependencies on legacy infrastructure that was originally designed for strategic weapons (i.e. it was intended to work at peak performance, just once). The payloads evolved to reflect the launch system constraints, so very expensive, one-of-a-kind comsats and earth resources satellites, each of them a bespoke design (or at most one of a dozen or so).

SpaceX isn't building missiles; it's optimizing for reliability and cost (which means reusability). More like airliners than missiles. This doesn't mean low performance (the efficiency and power density of a modern civil airliner turbofan would have been a jaw-dropper to 1940s military aviation engineers) but it does mean the performance goals are different.

I am still extremely skeptical that Heavy/Starship will facilitate a Mars colony ... but that's because I'm skeptical about the economics and practicalities of building an off-planet colony when the externalities we normally take for granted (like a compatible biosphere) aren't available and nobody's really done the necessary R&D work on self-contained biospheres -- even the ISS is effectively an open-loop system dependent on constant resupply. (Biology and ecology are much harder than they look to a naive outsider.)