> We're not talking about exotic and expensive varieties of steel though.
4340 steel isn't exotic. It's one of the most commonly used grades of steel out there, and it's much cheaper than titanium. There are steels out there with significant stronger yield strengths too. Meanwhile the highest yield strength of any Ti alloy is <1300MPa.
Titanium is still a really great material in certain applications. But it's not magic. You have to use it intelligently in the right application to get a benefit from it.
The family of materials we call steel is so fantastic, it almost a shame it’s so ubiquitous that we take it for granted. If it were invented today the front page of HN would be loaded with stories of this miracle material.
The newest generation most advanced spaceships are made from steel, see Starship.
When you go to both maximum cold (cryo fuel), and you go to maximum (reentry heat) then steel is amazing.
Aluminum would turn to butter on reentry, it would require a massive amount of heat shielding. Titanium alloys would have same issue.
Titanium alloy also become to brittle in deep cryo.
So steel beats everything in this demanding application. Its amazing.